Well, W'ON, I um... looked it up, and .. er... it .. ah, appears that ..um .. it's ... er .. in the Dick'n'harry:

um
// for defs 1 and 3, // , // for def. 2
--interjection 1. (an indication of hesitation or inarticulateness). 2. (an expression of doubt, pensiveness, etc.).
--phrase (ummed; umming) 3. um and ah, Colloquial a. to be indecisive. b. to prevaricate.

er
// , // interjection (the written representation of an inarticulate sound made by a speaker when hesitating).

uh
// , // interjection (a written representation of a sound made by a speaker when hesitating): would you, uh, sort of, uh, like to dance? [imitative of various inarticulate sounds] (from www.macquariedictionary.com.au)

Do that make it word, Juan .. er, W'ON?