Kniffen rhymes with:
sniffen, giffen, griffen, griffon, sniffen, stiffen, acetaminophen, altenhofen, carstarphen, dalfen, deafen, dextrathoraphan, dolphin, draffen, entoffen, farfen, geffen, giffen, griffen, griffon, hafen, hanifen, hyphen, ibuprofen, lafon, ludwigshafen, mcguffin, mcmuffin, morphin, muffin, offen, often, orphan, paraffin, siphon, sniffen, soften, steffan, steffen, stephan, stiffen, sutphen, syphon, tamoxifen, toughen, xenophon
Kniffen sounds like:
kampen, kampman, kampmann, kempen, kemppainen, kneebone, kniffin