[kpp_kpp]

why oh why would you want to do that?

brr, bys, cry, cwm, dry, fly, fry, gym, gyp, hmm, hyp, nth, pht, ply, pry, pyx, shh, shy, sky, sly, spy, sty, syn, thy, try, tsk, why, wry, wyn

[null and void]

For extra points a 5 letter word with 'w' as a vowel...