diff --git a/hgext/purge.py b/hgext/purge.py
--- a/hgext/purge.py
+++ b/hgext/purge.py
@@ -118,8 +118,8 @@ def _check_fs(ui, repo):
     # notice a modified README file if the user ran "hg purge readme"
     modified, added, removed, deleted = repo.status()[:4]
     if modified or added or removed or deleted:
-        if not util.checkfolding(repo.path) and not ui.quiet:
-            ui.warn(_("Purging on name mangling filesystems is not "
+        if not util.checkcase(repo.path) and not ui.quiet:
+            ui.warn(_("Purging on case-insensitive filesystems is not "
                       "fully supported.\n"))
         raise util.Abort(_("outstanding uncommitted changes"))
 
diff --git a/mercurial/commands.py b/mercurial/commands.py
--- a/mercurial/commands.py
+++ b/mercurial/commands.py
@@ -643,7 +643,7 @@ def debugfsinfo(ui, path = "."):
     file('.debugfsinfo', 'w').write('')
     ui.write('exec: %s\n' % (util.checkexec(path) and 'yes' or 'no'))
     ui.write('symlink: %s\n' % (util.checklink(path) and 'yes' or 'no'))
-    ui.write('case-sensitive: %s\n' % (util.checkfolding('.debugfsinfo')
+    ui.write('case-sensitive: %s\n' % (util.checkcase('.debugfsinfo')
                                 and 'yes' or 'no'))
     os.unlink('.debugfsinfo')
 
diff --git a/mercurial/dirstate.py b/mercurial/dirstate.py
--- a/mercurial/dirstate.py
+++ b/mercurial/dirstate.py
@@ -76,11 +76,11 @@ class dirstate(object):
         elif name == '_checkexec':
             self._checkexec = util.checkexec(self._root)
             return self._checkexec
-        elif name == '_folding':
-            self._folding = not util.checkfolding(self._join('.hg'))
-            return self._folding
+        elif name == '_checkcase':
+            self._checkcase = not util.checkcase(self._join('.hg'))
+            return self._checkcase
         elif name == 'normalize':
-            if self._folding:
+            if self._checkcase:
                 self.normalize = self._normalize
             else:
                 self.normalize = lambda x: x
diff --git a/mercurial/merge.py b/mercurial/merge.py
--- a/mercurial/merge.py
+++ b/mercurial/merge.py
@@ -460,7 +460,7 @@ def update(repo, node, branchmerge, forc
         action = []
         if not force:
             _checkunknown(wc, p2)
-        if not util.checkfolding(repo.path):
+        if not util.checkcase(repo.path):
             _checkcollision(p2)
         action += _forgetremoved(wc, p2, branchmerge)
         action += manifestmerge(repo, wc, p2, pa, overwrite, partial)
diff --git a/mercurial/util.py b/mercurial/util.py
--- a/mercurial/util.py
+++ b/mercurial/util.py
@@ -839,7 +839,7 @@ def groupname(gid=None):
 
 # File system features
 
-def checkfolding(path):
+def checkcase(path):
     """
     Check whether the given path is on a case-sensitive filesystem