The Collaborative International Dictionary
To let on
Let \Let\, v. i.
To forbear. [Obs.]
--Bacon.-
To be let or leased; as, the farm lets for $500 a year. See note under Let, v. t.
To let on, to tell; to tattle; to divulge something. [Low]
To let up, to become less severe; to diminish; to cease; as, when the storm lets up. [Colloq.]
Usage examples of "to let on".
I know that she noticed the alacrity with which I did so, but I did nothing to let on that I knew she had seen it.
Longarm spoke Spanish better than he wanted to let on to any Mexican who called him a stranger so sarcastically.