I usually save my persnickety word bullshit for this glorious English language of ours, but I'm branching out.
Almost nothing drives me as nuts as hearing a sports announcer, TV talking head, or bad sitcom character say that two guys are going mano y mano [pronounced "mah-no eee mah-no"].
That means two combatants are going hand-in-hand. Technically, it means "hand and hand." I've heard the phrase used by Spanish speakers, in the sense that we say two things go "hand-in-hand" [together]. But they may have just borrowed it from the English [probably not; most of those catch-phrases seem to have been in use throughout the west], since many of the speakers are bilingual.
The Spanish phrase, the venerable, much-loved, macho phrase used to describe combatants going at each other in their organic, elemental way, is mano a mano -- hand-to-hand [again, technically probably closer to "hand-at-hand" . . . .] Pronounced "Mah-no aah mah-no".
Fuckers. Dirty, dirty fuckers