nepali language aka khas language is a mixture from sanskrit,indian and persian i.e urdu(recently after british empire). the language that has directly derived from sanskrit are tamil kannad etc. nepali language as we speak today has been changed a lot esp in writing if you look at the the writings 200 yrs ago you'll know the difference. baun and chhetri were called khas cause they originally came from khasmir(today's kasmir and surronding area including kumau,Garhwal etc. khas picked perisan words while travelling from mid europe to khasmir and sanskrit and punjabi when they reached khasmir. that's why we find many words similiar.