Green’s Dictionary of Slang

grits n.1

[lit. + fig. uses of SE grits, coarse oatmeal, a trad. Southern or black food]

[1950s+] (US black) any form of food.

In phrases

get one’s grits (v.)

[1960s] (US black) to enjoy something.

up in someone’s grits

[2000s] (US black) of a man, having sexual intercourse.