From Latin *pertum*, a reduced form of *appertum* (past participle of *apperire*, "to be near/open toward"). In Vulgar Latin it was also influenced by the adverbial use of *prope* ("near"), eventually settling into Old Portuguese as *perto* with its modern meaning of proximity.

Brazilians frequently pair *perto* with *de* to form the preposition *perto de* ("close to / near"). You'll hear it constantly for giving directions: *"Fica perto do metrô"* ("It's near the metro"). Watch out for the false friend trap with Spanish *cierto* ("certain") — they look vaguely similar but mean completely different things.