Not to look at gift horse in the mouth

Question

I understand the meaning of the saying and the context it’s used in.

What I don’t understand is why you would look a horse (or gift horse) in the MOUTH. What is special about its mouth?

In: Other

Answer 1

I remember this being one of the questions in my adult autism assessment. I stared at her blankly without an answer when I was asked this. Reading the responses is cracking me up.