let on

verb

1. to allow (something, such as a secret) to be known; reveal

   he never let on that he was married

2. (tr) to cause or encourage to be believed; pretend

Idioms and Phrases

Reveal one's true feelings or a fact, allow something to be known, as in Don't let on that you met her before . This usage is probably a shortening of let it on someone . [c. 1700]

Pretend, as in He let on that he was very angry, but in fact he didn't care a bit . [First half of 1800s] Also see let in on .