the wiser

[keannu]

At first, I interpreted this as "the more wise person", but later found out it means "unaware of something". How come it means such a thing?

st29)Every security system, without exception, needs trusted people to function, through these people are not necessarily trusworthy. The person who installs your front-door lock is, by definition, a trusted person. You have no choice but to trust him, but he could make a copy of your key for himself, and you wouldn't be the wiser....

 

[Raymott]

At first, I interpreted this as "the more wise person", but later found out it means "unaware of something". How come it means such a thing?

st29)Every security system, without exception, needs trusted people to function, through these people are not necessarily trusworthy. The person who installs your front-door lock is, by definition, a trusted person. You have no choice but to trust him, but he could make a copy of your key for himself, and you wouldn't be the wiser....

It doesn't. "The wiser" means "aware of something". You've got it the opposite way around.
"you wouldn't be the wiser" = "you wouldn't be any the wiser", "you'd be none the wiser". These are all variants.
This is an idiom where we insert "the" when it appears that it shouldn't be there.
Are you any the wiser for having read my reply?

 

[keannu]

Does it come from the nuance of "having wisdom = knowing something or situation"? I guess so.

 

[Raymott]

Does it come from the nuance of "having wisdom = knowing something or situation"? I guess so.

Yes.