Don't know about "guTTle", but I vividly recall "guddle" (well, that's what it sounded like anyway) as meaning : to dither about or shilly shally aimlessly, usually where water was concerned... a bit like plowter, but more pointed (eh?) That was around central Scotland, below Forth. Oh, and "guddling" was a technique used to tickle fish such as trout when engaged in the piscatorial art... without a licence. God alone knows what that'll do for the context of the song though.