hi, wordwind - welcome to the nuthouse!

I can think of a few off the cuff (or is that cwfff?)

dwr = water
swn = sound

(those two should have a 'to' or roof over the 'w' - like this letter's: û - but I can't seem to find that in the standard character sets...)

ffrwd = misty, damp (I think)
twr = tower
twll = hole
bwlch = gap (in hills etc), pass
hwn = that

Perhaps Rod and others will think of some more. What's your interest in Welsh words derived from?