Swoleshamed by one of my best friends

First off, I would like to apologize for my lack of using the dialect of the iron temple, I am too flustered to focus on achieving the level of proficiency required in the English arts.

Anyways, I've been going to the gym for about a year and a half now. My roomate who also happens to be one of my best friends has been fine with it, it was no big deal and he seemed to be fine with me bettering myself both physically and mentally by going to the gym.

Well today was different. I got back from the gym and he said...he said "Wow you really are a 'tool' now aren't you?" I looked at him in shock, I did nothing to trigger him in any way. We are the chillest roomates you can imagine. This hurt me, all this work that I have been doing to better myself and he simply casts it aside by calling me a tool? I don't even take my worship at the iron temple that seriously. I haven't knowingly done anything to him or anyone else to cause trouble. Sure, my confidence has increased a little since I started working out but I'm still the same nerdy guy with an awkward sense of humor. I certainly am no "tool." I finally understand my brothers and sisters, I finally understand why this subreddit exists and it hurts.