Though i've only heard this used in parts of Dublin, Ireland, it may be used elsewhere too.
This word is derived from the Acronym. N.I.G(s). which stands for Not In Goal(s).
Basically, when you go to play football casually with friends, and there's no outright goalkeeper among you, no one ever wants to be in net. outfield players, naturally, want to play outfield. So, this game developed to decide who would be the first to go in net on any particular day.
It works like this. Once you are in view of the goalposts, and you think of it, you may proclaim ' NIGS!! '. the last person in the group to hear you and do likewise is the first person to go in net.
Having forgotten that the word 'nigs' stood for an acronym, or that the game had a very specific setting, many people just started using nigs for everything.
If someone asks a group of people to do something, one of them may simply shout 'nigs' and the last person to do likewise is usually pressured into doing whatever it is.
synonyms: not it