Excusing oneself

What’s the actual meaning of the expression “I will excuse myself ”?

I’ve thought of it as kind of a joking expression about doing something that would actually require the excuse of someone else in a more formal situation, but I figure that need not actually be the case.

Solution 1:

No, it's not meant as a joke at all.

The phrase " to excuse oneself" refers to the act of saying "Excuse me" and leaving.

Ex. I excused myself and stepped out of the room.

Ex. "If anyone has to leave early, please feel free to excuse yourself."

In direct speech, it's an expression used to be polite when you leave early.

Ex. "I'm not feeling so good today so I'll (have to) excuse myself from the meeting."

Solution 2:

Nothing joking in this. Excuse being transitive, takes two persons.

The one being 'excused' is 'myself' here. The one excusing is the person being addressed.

One can read this as: 'If you may so permit, I will consider myself excused (by you).'