1552, from M.E. whittel "a knife" (1404), variant of thwittle (1390), from O.E. þwitan "to cut," from P.Gmc. *thwitanan (cf. O.N. þveita "to hew").
I just posted this in the wrong thread and had to delete it and re-post it, so I'm not sure I can remember what I had originally posted.
Someone had mentioned this word (by way of another language), so I thought I'd post it here.
Somehow I was under the impression all these years that this word had onomatopoetic origins...