"This is tantamount to treason!" Yes, we all know what it means. But, uh, what does it mean, exactly?
I think most readers will agree that it means something like "this is an equivalent of treason". But does anyone have a clue as to the etymology of this word? I certainly don't.
But as it's my job here to guess, I will put forth a feeble Greek origin to the tanta- prefix. But -mount doesn't sound very Greek to me. This is one of those words where the deeper I get into guessing, the deeper I get in the muck. So let's find out the truth while we still can...
Yeah, it's a hybrid. But no, not Greek. "Tant" means 'so much, so great' and comes from the Latin tantum and "amount" apparently comes from the Old French amunter, a variant of amonter. You say amonter and I say amunter, let's call the whole thing... uh, sorry--I got distracted.
(P.S.--I tried to find a suitable image, but nothing quite worked. However, I'm open to suggestions...)