an extremely annoying, persistent pest
Ele liga dez vezes por dia para a mesma coisa; é um chato de galocha.
He calls ten times a day about the same thing; he's a real pest.
A galocha is a rubber overshoe once worn over your shoes to keep out mud and rain. Placed around the 1950s, the expression intensifies chato ("annoying") along two lines that sources give together: a galosh is tough and hard to peel off — like a pest who won't let go — and it evokes the inconsiderate visitor who tramps into someone's home still wearing galoshes, dripping and dirtying everything.
Sources: Só Português, Dicionário Popular.
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