I've heard it claimed by Harpal Brar in a podcast with Caleb Maupin (1:38:47) that the term "Stalinism" was invented by Trotsky, and that Stalin never wanted Stalinism and never claimed it as an ideology, and that all his life he claimed to be merely a pupil of Lenin. The latter I am certain of, you can see this pretty clearly in Foundations of Leninism. The former however, Trotsky inventing the term "Stalinism", I don't know. A cursory look at the Trotsky archive on marxists.org yields his earliest use of term as in 1926 in https://www.marxists.org/archive/trotsky/works/britain/ch10.htm
Overall a rather difficult thing to prove conclusively that he invented the term -- but it wouldn't surprise me.
P.S. this is new talk page is much easier, cheers!