to split hairs, to look for trouble where there is none
A professora ficou procurando chifre em cabeça de cavalo, mas não encontrou nada.
The teacher was splitting hairs while grading, but couldn't find anything.
The expression has no documented historical origin; its force comes from the absurd picture it paints. A horse simply has no horns, so to go looking for a chifre em cabeça de cavalo — "a horn on a horse's head" — is to hunt for something that cannot possibly be there.
Falando's Idiom Trainer teaches you to recognize idiom meanings and create sentences using them, so you can speak like a Brazilian.
