This is the part of AWAD that I enjoy the most. The "where, who or how" various terms came into the language is intriguing. Having visited England many times I wondered at the differences of terms for things. Bobby is
just one. Anu told us where the term comes from.

In the same vein where does the term "cop" stem from for an american policeman?

Does anyone know?

I found http://www.uselessknowledge.com/word/cop.shtml

There's an urban legend about this at
http://www.urbanlegends.com/language/etymology/cop_etymology_of.html that refers to an acronym (probably "constable on patrol").


k

Cop is a shortened form of “copper” and was in use in the UK before it was in the US. It stems from the slang verb “to cop”. Cop is used in various combinations such as “cop out” (evading one’s responsibilities), “not much cop” (of little use) and “it’s a fair cop” (you’ve caught me bang to rights). The last example connects with the custodian of the law, or peeler (same derivation as bobby) and the derivation of the verb “to cop” in this sense is obscure but may be related to the Old French verb “caper” meaning to seize. (Thank you, OED!)

Edit: Drat, FF, you beat me to it with a really good link!

dxb

Quinion says much the same:

http://www.worldwidewords.org/qa/qa-cop2.htm

Further to this, how did policemen come to be called "pigs" and "the fuzz"?

I'm guessing "the fuzz" might refer to the hair - do policemen have to have very short hair or even buzz cuts?