He never let on that he was married.

[wanabee]

Dear all,

He never let on that he was married.

The above sentence is the example Wordreference dictionary gives for the idiom 'let on'.
Could someone give me any clues about how 'let on' can mean 'reveal' or 'pretend'?
I would appreciate any comments.

let on
vb (adverb; when tr, takes a clause as object) informal

• to allow (something, such as a secret) to be known; reveal: he never let on that he was married
• (transitive) to cause or encourage to be believed; pretend

 

[JulianStuart]

The key word in your question is, I think, "idiom". The WRF dictionary has one definition

a group of words whose meaning cannot be predicted from the meanings of the constituent words,

The obvious guess as to how the "let on" arose would be with the meaning of the main word let: to allow (you to know).

 

[wanabee]

Thank you very much, Julian!