Middle English roten, from Old English rotian, of animal substances, "to decay, putrefy, undergo natural decomposition" (intransitive), also of vegetable matter," from Proto-Germanic *rutjan (source also of Old Saxon roton, Old Norse rotna, Old Frisian rotia, Middle Dutch roten, Dutch rotten, Old High German rozzen "to rot," German rößen "to steep flax"), from stem *rut-. Related: Rotted; rotting.
By c. 1200 as "fester or decay morally, become morally corrupt." Transitive sense of "cause decomposition in" is from late 14c. To rot in prison (mid-14c.) suggests wasting disease.
suffix used to make jocular or familiar formations from common or proper names (soccer being one), first attested 1860s, English schoolboy slang, "Introduced from Rugby School into Oxford University slang, orig. at University College, in Michaelmas Term, 1875" [OED, with unusual precision].
<a href="https://www.etymonline.com/word/rotter">Etymology of rotter by etymonline</a>
Harper, D. (n.d.). Etymology of rotter. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/rotter