Bill and coo is an idiom that has been in use since the 1700s. We will examine the meaning of the idiom bill and coo, where it came from, and some examples of its use in sentences.
To bill and coo is to kiss and caress quietly, to speak loving words quietly. One will often bill and coo during courtship. Young lovers often bill and coo. The image is of two doves preening each other and making soft noises. The idiom bill and coo is found in writings as early as the 1760s. The word bill in bill and coo is a verb that means to stroke beaks together. Related phrases are bills and coos, billed and cooed, billing and cooing.
The answer, of course, is that it would cost the film its central comic device: Ron’s cosy chit-chats with the Klan’s oblivious Grand Wizard David Duke (Topher Grace), where the pair bill and coo like late-night lovebirds. (The New Statesman)
They kick and scream, and are often indulged by parents who glare at you with sheer hatred if you do anything other than bill and coo at them. (The Guardian)
“It has the feeling that one has when you see these pieces — a very intimate, personal experience in the same way that billing and cooing are in a romantic sense.” (The Los Angeles Times)
As I departed, one billing and cooing pair had propped a smartphone against a potted plant to take a romantic selfie in the vast plaza. (The Houston Chronicle)