Wouldn't even pay attention to the packs of feral Iraqi hounds that yap and howl all through the night when people walk by.
c.1600, probably of imitative origin. Originally in reference to dog sounds; meaning "to talk idle chatter" is first recorded 1886. Related: Yapped; yapping.
The mouth; bazoo: every time you open your yap to say something (1900+)verb
To talk, esp idly or naggingly; yammer: You've been yapping away (1886+)Related Terms
[probably echoic, and similar to the sense ''yelp,'' esp as a small dog does]