nit

Concise Oxford English Dictionary © 2008 Oxford University Press:
nit1

▶noun informal

• 1 the egg or young form of a louse or other parasitic insect, especially the egg of a human head louse.

• 2 Brit. a stupid person.

– derivatives
nitty adjective.

– origin OE hnitu, of W. Gmc origin.

Concise Oxford English Dictionary © 2008 Oxford University Press:
nit2

▶exclamation Austral. informal used as a warning that someone is approaching.

– phrases
keep nit keep watch.

– origin C19: prob. from nix.