Seeking a citation, I found the following:
To see every day how people get the name ‘genius' just as the wood-lice in the cellar the name ‘millipede' - not because they have that many feet, but because most people don't want to count to 14 - this has had the result that I don't believe anyone any more without checking.
- Georg Christoph Lichtenberg, Lichtenberg: Aphorisms & Letters (1969), 48, translated by Franz H. Mautner and Henry Hatfield.
...on this horribly-formatted website. Google Books verifies.
(P.S. Note that the original is in German.)
My source was this Roger Kimball article. I just found the book that Kimball references on Google Books and it doesn't seem to contain any version of that quote, so for now I'd guess that your version is more accurate. Ideally we'd want to find the original German version.
(Since there didn't seem to be one for this month, and I just ran across a nice quote.)
A monthly thread for posting any interesting rationality-related quotes you've seen recently on the Internet, or had stored in your quotesfile for ages.