Originally Posted by
Capt. Ido Nos
I've been partial to the idea of "fillyfooler" having 'fooler' as the base of the word, with 'filly' as the modifier. You are a fooler, and a filly at that. Fooler in this case leaning towards the "idiot/simpleton" definitions of fool, as opposed to the connotations of 'fooling around'. So, we end up with this being an insult in which you call into question their base intelligence, and maturity at that.
Also, just for kicks I threw fooler into google definition, and it said that a fooler was a pacifier, so there's that.