Entries linking to sadist
"love of cruelty," especially as evidence of a subconscious lust that the cruelty satisfies, 1888, from French sadisme, from the name of Count Donatien A.F. de Sade (1740-1815). Not a marquis, though usually now called one, he was notorious for the cruel sexual practices described in his novels.
Variant -ister (as in chorister, barrister) is from Old French -istre, on false analogy of ministre. Variant -ista is from Spanish, popularized in American English 1970s by names of Latin-American revolutionary movements.