patas negras

patas negras - black feet...someone who has black feet is the "lover", a cheater. This expression comes from Lota, (not too far from Concepción). There has been a carbon mine there since the mid-nineteenth century, although it's been closed since the 1990s. The miners worked in shifts, some worked night shifts, others, day shifts. If a miner came home to his house and family and saw black foot prints in his house then he knows his wife was cheating on him with another miner who has the opposite shift. And clearly the other guy has black feet from working in the mine.

Esa mina es una patas negras maraca. Se está comiendo el pololo de su amiga.
That chic's a slutty patas negras. She's getting it on with her friend's boyfriend.

Chilenismo, coloquial