What does peanut butter have to do with spiders?

They share quite a few letters in Greek? The genus name for peanut is arachis (from Greek arakhis (alternate arakis) 'a kind of leguminous plant, chickling', diminutive of arakos 'legume'. Spider in Greek is arakhne. The real question, which I neglected to ask, is why the English word is incorrectly formed. The oblique cases of arakhis are formed from the stem arakhid- (e.g., the genitive is arakhidos), so the term is more pedantically formed as arachidobutyrophobia.

Full disclosure: I am not now, nor have I ever been, allergic to or afraid of peanut butter, but I now know that some people are either one or the other or both.

Ceci n'est pas un seing.