Green’s Dictionary of Slang

(S.Afr.) a derog. term for a person of Portuguese descent.

1975		informant in DSAE (1996).
1989		Style July 41: To the average South African in Blairgowrie a porra .. is a porra. Half the time the South African’s not aware that the person he’s referring to is actually Greek ... Porra is a swearword in Portuguese, what a labourer building a house says when he drops a brick on his foot. One theory claims the term was first used by upper class Portuguese to denote the lower orders, who were always shouting ‘Porra!’ Another theory claims the word comes from the lazy Afrikaans pronunciation ‘Porregees’ [DSAE].