deep throat
Concise Oxford English Dictionary © 2008 Oxford University Press:
deep throat
▶noun a person who anonymously supplies information about covert or illegal action in the organization where they work.
– origin 1970s: the title of a pornographic film of 1972, first applied in this sense as the name (‘Deep Throat’) of an informant in the Watergate scandal.
'deep throat' also found in these Oxford entries:
