diff --git a/core/modules/layout_discovery/layout_discovery.layouts.yml b/core/modules/layout_discovery/layout_discovery.layouts.yml
index 98b1ed6..d1b0e5a 100644
--- a/core/modules/layout_discovery/layout_discovery.layouts.yml
+++ b/core/modules/layout_discovery/layout_discovery.layouts.yml
@@ -15,14 +15,14 @@ layout_twocol:
   template: layout--twocol
   library: layout_discovery/twocol
   category: 'Columns: 2'
-  default_region: left
+  default_region: first
   regions:
     top:
       label: Top
-    left:
-      label: Left
-    right:
-      label: Right
+    first:
+      label: First
+    second:
+      label: Second
     bottom:
       label: Bottom
 
@@ -36,16 +36,16 @@ layout_twocol_bricks:
   regions:
     top:
       label: Top
-    left_above:
-      label: 'Left above'
-    right_above:
-      label: 'Right above'
+    first_above:
+      label: 'First above'
+    second_above:
+      label: 'Second above'
     middle:
       label: Middle
-    left_below:
-      label: 'Left below'
-    right_below:
-      label: 'Right below'
+    first_below:
+      label: 'First below'
+    second_below:
+      label: 'Second below'
     bottom:
       label: Bottom
 
@@ -55,16 +55,16 @@ layout_threecol_25_50_25:
   template: layout--threecol-25-50-25
   library: layout_discovery/threecol_25_50_25
   category: 'Columns: 3'
-  default_region: left
+  default_region: second
   regions:
     top:
       label: Top
-    left:
-      label: Left
-    middle:
-      label: Middle
-    right:
-      label: Right
+    first:
+      label: First
+    second:
+      label: Second
+    third:
+      label: Third
     bottom:
       label: Bottom
 
@@ -74,15 +74,15 @@ layout_threecol_33_34_33:
   template: layout--threecol-33-34-33
   library: layout_discovery/threecol_33_34_33
   category: 'Columns: 3'
-  default_region: left
+  default_region: first
   regions:
     top:
       label: Top
-    left:
-      label: Left
-    middle:
-      label: Middle
-    right:
-      label: Right
+    first:
+      label: First
+    second:
+      label: Second
+    third:
+      label: Third
     bottom:
       label: Bottom
diff --git a/core/modules/layout_discovery/layouts/threecol_25_50_25/layout--threecol-25-50-25.html.twig b/core/modules/layout_discovery/layouts/threecol_25_50_25/layout--threecol-25-50-25.html.twig
index a944b57..6475695 100644
--- a/core/modules/layout_discovery/layouts/threecol_25_50_25/layout--threecol-25-50-25.html.twig
+++ b/core/modules/layout_discovery/layouts/threecol_25_50_25/layout--threecol-25-50-25.html.twig
@@ -26,21 +26,21 @@
       </div>
     {% endif %}
 
-    {% if content.left %}
-      <div class="layout-region layout-region--left">
-        {{ content.left }}
+    {% if content.first %}
+      <div class="layout-region layout-region--first">
+        {{ content.first }}
       </div>
     {% endif %}
 
-    {% if content.middle %}
-      <div class="layout-region layout-region--middle">
-        {{ content.middle }}
+    {% if content.second %}
+      <div class="layout-region layout-region--second">
+        {{ content.second }}
       </div>
     {% endif %}
 
-    {% if content.right %}
-      <div class="layout-region layout-region--right">
-        {{ content.right }}
+    {% if content.third %}
+      <div class="layout-region layout-region--third">
+        {{ content.third }}
       </div>
     {% endif %}
 
diff --git a/core/modules/layout_discovery/layouts/threecol_25_50_25/threecol_25_50_25.css b/core/modules/layout_discovery/layouts/threecol_25_50_25/threecol_25_50_25.css
index fc35a05..3570cf5 100644
--- a/core/modules/layout_discovery/layouts/threecol_25_50_25/threecol_25_50_25.css
+++ b/core/modules/layout_discovery/layouts/threecol_25_50_25/threecol_25_50_25.css
@@ -4,16 +4,16 @@
 }
 
 .layout--threecol > .layout-region,
-.layout--threecol > .layout-region--middle {
+.layout--threecol > .layout-region--second {
   flex: 0 1 100%;
 }
 
 @media screen and (min-width: 40em) {
-  .layout--threecol > .layout-region--left,
-  .layout--threecol > .layout-region--right {
+  .layout--threecol > .layout-region--first,
+  .layout--threecol > .layout-region--third {
     flex: 0 1 25%;
   }
-  .layout--threecol > .layout-region--middle {
+  .layout--threecol > .layout-region--second {
     flex: 0 1 50%;
   }
 }
diff --git a/core/modules/layout_discovery/layouts/threecol_33_34_33/layout--threecol-33-34-33.html.twig b/core/modules/layout_discovery/layouts/threecol_33_34_33/layout--threecol-33-34-33.html.twig
index fc8da1b..e5aa061 100644
--- a/core/modules/layout_discovery/layouts/threecol_33_34_33/layout--threecol-33-34-33.html.twig
+++ b/core/modules/layout_discovery/layouts/threecol_33_34_33/layout--threecol-33-34-33.html.twig
@@ -26,21 +26,21 @@
       </div>
     {% endif %}
 
-    {% if content.left %}
-      <div class="layout-region layout-region--left">
-        {{ content.left }}
+    {% if content.first %}
+      <div class="layout-region layout-region--first">
+        {{ content.first }}
       </div>
     {% endif %}
 
-    {% if content.middle %}
-      <div class="layout-region layout-region--middle">
-        {{ content.middle }}
+    {% if content.second %}
+      <div class="layout-region layout-region--second">
+        {{ content.second }}
       </div>
     {% endif %}
 
-    {% if content.right %}
-      <div class="layout-region layout-region--right">
-        {{ content.right }}
+    {% if content.third %}
+      <div class="layout-region layout-region--third">
+        {{ content.third }}
       </div>
     {% endif %}
 
diff --git a/core/modules/layout_discovery/layouts/threecol_33_34_33/threecol_33_34_33.css b/core/modules/layout_discovery/layouts/threecol_33_34_33/threecol_33_34_33.css
index ab261d0..f01e55c 100644
--- a/core/modules/layout_discovery/layouts/threecol_33_34_33/threecol_33_34_33.css
+++ b/core/modules/layout_discovery/layouts/threecol_33_34_33/threecol_33_34_33.css
@@ -8,9 +8,9 @@
 }
 
 @media screen and (min-width: 40em) {
-  .layout--threecol-33 > .layout-region--left,
-  .layout--threecol-33 > .layout-region--middle,
-  .layout--threecol-33 > .layout-region--right {
+  .layout--threecol-33 > .layout-region--first,
+  .layout--threecol-33 > .layout-region--second,
+  .layout--threecol-33 > .layout-region--third {
     flex: 0 1 33%;
   }
 }
diff --git a/core/modules/layout_discovery/layouts/twocol/layout--twocol.html.twig b/core/modules/layout_discovery/layouts/twocol/layout--twocol.html.twig
index 66454c5..2ad6740 100644
--- a/core/modules/layout_discovery/layouts/twocol/layout--twocol.html.twig
+++ b/core/modules/layout_discovery/layouts/twocol/layout--twocol.html.twig
@@ -23,15 +23,15 @@
       </div>
     {% endif %}
 
-    {% if content.left %}
-      <div class="layout-region layout-region--left">
-        {{ content.left }}
+    {% if content.first %}
+      <div class="layout-region layout-region--first">
+        {{ content.first }}
       </div>
     {% endif %}
 
-    {% if content.right %}
-      <div class="layout-region layout-region--right">
-        {{ content.right }}
+    {% if content.second %}
+      <div class="layout-region layout-region--second">
+        {{ content.second }}
       </div>
     {% endif %}
 
diff --git a/core/modules/layout_discovery/layouts/twocol/twocol.css b/core/modules/layout_discovery/layouts/twocol/twocol.css
index c017eec..13d32fd 100644
--- a/core/modules/layout_discovery/layouts/twocol/twocol.css
+++ b/core/modules/layout_discovery/layouts/twocol/twocol.css
@@ -8,8 +8,8 @@
 }
 
 @media screen and (min-width: 40em) {
-  .layout--twocol > .layout-region--left,
-  .layout--twocol > .layout-region--right {
+  .layout--twocol > .layout-region--first,
+  .layout--twocol > .layout-region--second {
     flex: 0 1 50%;
   }
 }
diff --git a/core/modules/layout_discovery/layouts/twocol_bricks/layout--twocol-bricks.html.twig b/core/modules/layout_discovery/layouts/twocol_bricks/layout--twocol-bricks.html.twig
index 267f2e8..764c4af 100644
--- a/core/modules/layout_discovery/layouts/twocol_bricks/layout--twocol-bricks.html.twig
+++ b/core/modules/layout_discovery/layouts/twocol_bricks/layout--twocol-bricks.html.twig
@@ -26,15 +26,15 @@
       </div>
     {% endif %}
 
-    {% if content.left_above %}
-      <div class="layout-region layout-region--left-above">
-        {{ content.left_above }}
+    {% if content.first_above %}
+      <div class="layout-region layout-region--first-above">
+        {{ content.first_above }}
       </div>
     {% endif %}
 
-    {% if content.right_above %}
-      <div class="layout-region layout-region--right-above">
-        {{ content.right_above }}
+    {% if content.second_above %}
+      <div class="layout-region layout-region--second-above">
+        {{ content.second_above }}
       </div>
     {% endif %}
 
@@ -44,15 +44,15 @@
       </div>
     {% endif %}
 
-    {% if content.left_below %}
-      <div class="layout-region layout-region--left-below">
-        {{ content.left_below }}
+    {% if content.first_below %}
+      <div class="layout-region layout-region--first-below">
+        {{ content.first_below }}
       </div>
     {% endif %}
 
-    {% if content.right_below %}
-      <div class="layout-region layout-region--right-below">
-        {{ content.right_below }}
+    {% if content.second_below %}
+      <div class="layout-region layout-region--second-below">
+        {{ content.second_below }}
       </div>
     {% endif %}
 
diff --git a/core/modules/layout_discovery/layouts/twocol_bricks/twocol_bricks.css b/core/modules/layout_discovery/layouts/twocol_bricks/twocol_bricks.css
index 9613e36..18a38f5 100644
--- a/core/modules/layout_discovery/layouts/twocol_bricks/twocol_bricks.css
+++ b/core/modules/layout_discovery/layouts/twocol_bricks/twocol_bricks.css
@@ -8,10 +8,10 @@
 }
 
 @media screen and (min-width: 40em) {
-  .layout--twocol-bricks > .layout-region--left-above,
-  .layout--twocol-bricks > .layout-region--right-above,
-  .layout--twocol-bricks > .layout-region--left-below,
-  .layout--twocol-bricks > .layout-region--right-below {
+  .layout--twocol-bricks > .layout-region--first-above,
+  .layout--twocol-bricks > .layout-region--second-above,
+  .layout--twocol-bricks > .layout-region--first-below,
+  .layout--twocol-bricks > .layout-region--second-below {
     flex: 0 1 50%;
   }
 }