These three words are very similar in English, Russian and Kazakh. At least the Russian set is considered inherited from PIE.
English - Russian - Kazakh crush - крушить (krushitь) - қырш (qyrsh) plash - плескать (pleskatь) - былш (bylsh) slap - шлёпать (shlёpatь) - шылп (shylp)
Noticable is that the second word in Kazakh looks more similar to English than Russian.
Some people explain it via onomatopoieia but at least the Russian set comes to PIE roots.
- крушить is from PIE kreu- "crush"
- плескать is from PIE plea̯- "flat", "wide", from pel- "full"
- шлёпать is from PIE leip- "sticky"
Deriving all these words from one proto-source seems impossible though (especially the Turkic ones). So I wonder whether Kazakh etymology of these words has been ever explained through borrowing?