I have no idea who came up with it, and when, but you're right, it's a very cool and cute word, and we amor Mikegasms, don't we???!!! ;) Lol!!! Michael must've been totally embarassed if someone confronted him with that word, of course, but he was aware of the effect he had on the ladies, so... I'm sure he just lol'd about it!
I think we made up that word ourselves. Like we just started randomly saying it. Haven't y'all realize that? And yeah I like that word. Just like I like saying the word," whatsittooya," followed por saying the funniest joke/phrase on the planet," that's what she said," or," that's what HE said."
It is a pretty cool word...and I don't know exactly who came up with 'Mikegasm'...I guess it's just like a meme...people make it...people see it...people share it...and just like that, the meme (or in this case, the word) is all over the internet. Heck, it's even in Urban Dictionary! Check it out!