You are confusing “cunnus” with “cuneus”, @DSeid 
The former does not mean “wedge”… (at least not literally, and the etymology has not been certainly established.) Etymology is uncertain but various dictionaries suggest related words meaning ditch, gash, slit…
Oh, well. “Cuneus” is still one theory of origin, but more likely is either the PIE root for “conceal” (as in a cover – which would make “sky” a cognate – “sky” originally meant “cloud”), or the PIE root for “cut” (as in a slit – which would make “scissors” and “shit”* cognates).
(*The shit/scissors connection is well established. It’s about how, when you shit, a piece of your body is being “cut” from the rest of your body.)
So our Proto-Indo-European-speaking forebears thought they were made of shit?
That actually very sad.
Eh, “pinch one off” is still used today. It’s the same connotation.
And it still helped as a study aid!