It’s been too long since I’ve done a word etymology. Okay, too long for me. But whatever.
Anyway, this week’s word is probable which, for the record, is not related to problem, the word that first led me here. Probable showed up in the late fourteenth century from the Old French probable and further back from the classical Latin probabilis—meaning provable. This isn’t that surprising since there are a lot of words out there where v turns into b or vice versa.
Yes, probabilis is related to our provable and prove. Prove is older than probable, having shown up in the late twelfth century as prouwe (less confusing when you learn about the connection between u, v and w). It comes from the Old French prover and classical Latin probare, which also happens to be the precursor to probabilis.
And the story doesn’t end there. Probare means to test or to prove worthy and comes from the also classical Latin probus, which means worthy, upright, virtuous. That word can be traced back to the Proto Indo European pro-bhwo—being in front. Pro- means in front of and and bhwo is from bhu-, to be (before you ask, yes, that’s its origin).
TL;DR: Probable and prove are related because b can be v and v can be w and the only thing more confusing that word origins is letter origins.
Ceisiwr Serith for information on Proto Indo European.
Orbis Latinus for information on Old French.