In Italian, 'puntiglio' means "a fine point," hence a verbal quibble, and is most likely the source of the English "punctilious." There developed in late 17th- and early 18th- century England a short-lived, fanciful word "pundigrion," which indeed was a term for what we now know as a pun. Since snappy monosyllables produced by breaking off pieces of longer words were all the rage back then, it is widely thought that this is how and where the word "pun" was created.
A pun is defined by Webster as "the humorous use of a word, or of words which are formed or sounded alike but have different meanings, in such a way as to play on two or more of the possible applications; a play on words."
In describing the various forms of verbal humor, The New Encyclopaedia Britannica refers to a pun as "two disparate strings of thought tied together by an acoustic knot." That analogy strikes a very pleasant cord !
Source - http://www.walshnet.com/walshnet/punster/puns.html