Incorrect spelling, explanation: aggree is a misspelling; probably a confusion made due to doubling another letter (e) in this word. The correct form is agree. It comes from Old French agreer, so the correct spelling of agree is taken directly from French.

Correct spelling, explanation: the word came to English from Old French agreer, which was a short version of the phrase a gré favorably. Alike French, the English form is spelled with one g instead of two, so agree is the correct form. Therefore aggree is a mistake. Because of its origins, agree is the only correct spelling.

Definition of agree:
verb, to admit somebody is correct
I didn’t agree with you at first, but now I think you were right.
This dress is perfect for these shoes, don’t you agree?

Incorrect spelling