diff --git a/src/common/gen/Configurator.py b/src/common/gen/Configurator.py
index 616b8c22d2..13ac3a2ee0 100644
--- a/src/common/gen/Configurator.py
+++ b/src/common/gen/Configurator.py
@@ -50,7 +50,7 @@ def __init__(
         self.__compiled_regexes = {}
 
         # Pre-defined exclusion sets for config processing
-        self.__excluded_prefixes = ("_", "PYTHON", "KUBERNETES_", "SVC_", "LB_", "SUPERVISOR_")
+        self.__excluded_prefixes = ("PYTHON", "KUBERNETES_", "NOMAD_", "SVC_", "LB_", "SUPERVISOR_")
         self.__excluded_vars = frozenset(
             {
                 "DOCKER_HOST",
@@ -112,6 +112,36 @@ def __init__(
         else:
             self.__variables = variables
 
+        # Allow a leading underscore prefix on env var names so that domain names
+        # starting with a digit can be configured (bash forbids var names starting
+        # with a digit, e.g. 1nteresting.io).  Users write _1nteresting.io_USE_...
+        # and we strip the single leading underscore here before any other processing.
+        stripped: Dict[str, str] = {}
+        stripped_origins: Dict[str, str] = {}  # new_key -> original key that set the current value
+        for k, v in self.__variables.items():
+            new_key = k.removeprefix("_")
+            if not new_key:
+                # Skip bare "_" or similar empty-after-strip keys
+                continue
+            if new_key in stripped:
+                prev_key = stripped_origins[new_key]
+                # Deterministic tie-break: the explicit (non-underscore) key wins over the
+                # underscore-prefixed form, independent of dict iteration order, so the same
+                # input always yields the same output. In a collision exactly one of the two
+                # keys equals new_key (the explicit form); the other is "_" + new_key.
+                explicit_wins = k == new_key
+                winner = k if explicit_wins else prev_key
+                self.__logger.warning(
+                    f"Variable collision after stripping leading underscore: {prev_key!r} and {k!r} both map to {new_key!r}, keeping {winner!r}"
+                )
+                if explicit_wins:
+                    stripped[new_key] = v
+                    stripped_origins[new_key] = k
+                continue
+            stripped[new_key] = v
+            stripped_origins[new_key] = k
+        self.__variables = stripped
+
         self.__multisite = self.__variables.get("MULTISITE", "no") == "yes"
         self.__servers = self.__map_servers()