I don’t know how, why, etc…

idiomPart ofknow

I don’t know how, why, etc… — idiom

1. Used to criticize someone's behavior by saying you cannot understand it.

1.idiom
Definition

Used to criticize someone's behavior by saying you cannot understand it.

Example

I don't know how you can eat that spicy food.

I don't know why she would lie about such a small thing.