Could care less
What you actually mean: Couldn’t care less
You want to say you care so little already that you couldn’t possibly care any less. When the Boston Celtics’ Ray Allen said, “God could care less whether I can shoot a jump shot,” we know he meant exactly the opposite because 1) God has other things on his mind, and 2) God is a Knicks fan. It’s safe to ignore these strict grammar rules.
Mano a mano
What you actually mean: Man-to-man
You don’t speak Spanish by adding vowels to the end of English words, as a columnist describing father–teenage son relationships seemed to think when he wrote, “Don’t expect long, mano a mano talks.” Mano a mano (literally, “hand to hand”) originated with bullfighting and usually refers to a knock-down, drag-out direct confrontation.