English word trollfic comes from English troll, English fic

Detailed word origin of trollfic

Dictionary entry	Language	Definition
troll	English (eng)	(transitive, intransitive, archaic) To sing the parts of in succession, as of a round, a catch, and the like; also, to sing loudly, freely or in a carefree way. [from the 16th c.]. (transitive, intransitive, obsolete) To move circularly; to roll; to turn. [from the 15th c.]. (transitive, obsolete) To send about; to circulate, as a vessel in drinking. (obsolete) A trolley.. A song whose parts [...]
fic	English (eng)	(slang, countable) A fictional story set within a preexisting fandom; a fanfic.
trollfic	English (eng)	(fandom slang) A work of fan fiction written to troll or annoy readers.