What does the “-eiro” ending mean in Portuguese?

Tesouro is treasure. Add -eiro / -eira and you get tesoureiro / tesoureira: the person who looks after the money. That suffix is one of Portuguese’s great job-making machines — it takes a thing and hands you back the person who deals with it, so a single noun you already know can unlock a whole shelf of occupations.

The pattern repeats everywhere: porta → porteiro (doorman), cozinha → cozinheiro (cook), jardim → jardineiro, peixe → peixeiro, sapato → sapateiro, and — with an older stem — pão → padeiro (baker). The same ending also names containers and plants: açucareiro (sugar bowl), cinzeiro (ashtray), bananeira (banana plant). Safest reading: “the thing associated with it.”