From Middle English -ling, from Old English -ling, from Proto-West Germanic *-ling, from Proto-Germanic *-lingaz, a nominal suffix, probably composed of Proto-Germanic *-ilaz (agent/instrumental/diminutive suffix) + Proto-Germanic *-ingaz (patronymic suffix).
Akin to Dutch -ling, German -ling, Icelandic -lingur, Gothic -𐌻𐌹𐌲𐌲𐍃 (-liggs). More at -le, -ing.