Myles uses an F-word

Now that REALLY got your attention.
No, not THE F-bomb, but one that is cause for alarm nonetheless.
It is a new word that I would like to say crept into his vocabulary, except that it didn't creep at all. It appeared--BOOM--fully fleshed out and ready for use. He was armed and dangerous with this word.
This afternoon we needed to go to the store. Myles was, of course, playing with his trains. He was not interested at all in my agenda, which required the very necessary step of putting on his sneakers. This is how the conversation went.
"Myles, please come here and let me put your sneakers on so we can go."
"No."
"My-eles. Please. Please come over here [he is physically moved to here], sit on the step and let me put your shoes on your feet."
"Nope."
"That's it! Myles, you are going to sit on this step, and I am going to put your sneakers on and we are going to the store."
"FINE!"
And that was with all the spoken and physical emphasis that was appropriate to his use of the word, but not appropriate to the situation. This was not fine, as in I feel fine, nor He's so fine, du-ang, du-ang, du-ang. No, this was FINE! resignation to my will under protest.