Quite so, mathprofrockstar.
I think I've found out why Doc used this dubious "stupid fellow" definition. There's an ambiguity in older editions of Chambers - mine from 1998, for instance - as to which meaning the 6-letter form applies to. This is clarified in more recent editions - 2008, for example - by the simple insertion of a semicolon, showing that it applies solely in the sense of a "blunder", not a "stupid fellow".