The adjective “anserine” is the epitome of the idiom “silly goose.” The original usage of the word is to describe anything related to or similar to a goose. The secondary meaning is “silly, stupid.” It’s uncertain if the teasing phrase “silly goose” is related to both definitions of “anserine,” but it’s a useful, albeit rare, adjective. The Latin “anserinus” comes from “anser,” meaning “goose,” and the suffix “-inus,” forming an adjective.