I was brought up in the warp-vs.-woof school too, but have encountered the weft along the way. I think I concluded it was a Britishism, but have no particular reason for thinking so, just an impression.

It brings to mind (for particular reason) another favorite w-word, which is "woots." I find it irresistable because it's part of the definition of an even more obscure word, to wit:

    "Ooly is woots"

(If you don't want to look them up, ooly is an ore derived from oolite [with a diacritical mark above the first o], a kind of iron found in meteorites, and woots is a kind of steel fabricated in old-time India, as of course the metallurgists among us will immediately recognize. To the best of my knowledge. I haven't looked them up lately either. )