[gmanley]

"cock" is not a very good example. Gash, as slang, is nowhere near as often used as "cock". Gash's meaning as "a long, deep cut" is, by far, the most used meaning. Whereas "cock", nowadays, the slang term is pretty much the only used meaning. Peach, rod, purse, knob, sheath, pocket, meat, etc. All these words have alternate slang meanings as well. Should we stop using their original meanings? Like I said in another comment, language is all about context. I've only ever heard 'gash' used as slang in the U.K. I would imagine a very large chunk of the English speaking population only know the non-slang meaning.