Why do sexual human parts have the same name as animals?

@damselfly The word "cock" also means a "tap", or "valve"; as in "stop-cock" (your home's water isolating valve), "try-cock" (a water-level test-valve); etc.

I wonder if the fire-arms "cock" was originally a fanciful comparison of its shape on a flint-lock gun, with the fleshy comb on a cockerel's head.

@ArishMell English has never had enough words. No wonder we've nicked words from other languages and resorted to using the same word for many things.

@damselfly Saves having to invent ones needlessly where the meaning is obvious from the context, I suppose.

The key to unlocking the curious alternative uses of a simple word is to examine its likely etymology and historical context.

What I do find far more strange is the fad for taking elegant words and mangling them into ugly, clumsy self-parodies, such as "inspi-ray-shun-ul" for "inspiring".

Or for using metaphorically, technical terms without really understanding them, sometimes changing unwittingly but totally the meaning of the message. The classic example is perhaps "epicentre". Also, so many musicians and art critics who ought know better, continue to use acoustic (adjective) for acoustics (noun), and resonant when they mean reverberant.

@bijouxbroussard No it is a very old word that was the word for the organ in English but has come to be regarded as unacceptable in polite society, that doesn't make it slang.

@ninalanyon The link you provided refers to it as a slang term. It’s not the medical term for the organ.

@bijouxbroussard True it isn't the medical term, but in English it is the older term for the organ. So not slang, merely not polite any more, too earthy for our modern sensibilities.

P.s. You can't believe everything you read on the Internet :-)

@LandOfOz It seems not.

Any good dictionary will give the etymology of a word, and my copy of Chambers Handy Dictionary gives these, showing no clear reference to shape.

Pen: Old French penne = a feather (for centuries, pens were quills.)

Pencil: Latin. penicillum = A painter's brush. Penicillin has the same root, presumably from the shape of the mould that is the medicine's source.

Penetrate : Latin. penetrare - penitus = inward.

Peninsula : Latin. paene* =almost, + insula = an island.

Penis: Latin. I.e. it was always that word since the Romans or their predecessors coined it. We might speculate that the Romans equated 'penis' and 'penetrare' but I will leave it to Latin scholars to verify or refute that.

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* Not to be confused with paean, a song or poem of triumph or joy; originally a Greek name for the god Apollo.