Proto-Indo-European *sem- "one, together with" became Sanskrit saṃgha (combined with *gʷʰen- "to strike"). Monier-Williams says this means "close contact or combination" and also "the whole community or collective body or brotherhood of monks". This word was borrowed into Middle Chinese, then into Japanese as sō "monk", then was combined with bon "ordinary" to form bonsō, bonzō (凡僧) "unranked priest" (bonsō also means "foolish monk" according to WWWJDIC). This was borrowed into Portuguese as bonzo, then into French, then into English as bonze.
The above etymological madness is brought to you by the AHD. As usual, the OED doesn't go this far; it just suggests that the Japanese word might be from Chinese fă-sze "teacher of the law". (Has this anything to do with 法則 fǎzé "rule, law"?)
In the meantime, *sem- became Russian samo- "self", which combined with varit' "to boil" (from *wer- "to burn") to form самовар samovar literally "self-boiler".