Tmc.
Terraria Community Forums
zeskorion
MrSandman
OMG, its so clear to me now.
TMC
*GASP* Safeman liked a comment on my profile 
TMC
also, it doesnt really have a specific meaning, the username was made by 9 year old me, and i liked that it was short, so i went with it. The one that someone guessed, that fits really good, is Terraria Mod Creator, but i really doubt that was the origional meaning.
Andromeda9a
Oh technical majestic car =TMC