Etymology of 'elfsturbating'
PIE *albʰós (white) > Proto-Germanic *albiz (elf) > Proto-West Germanic *albi > Old English ielf/ælf > elf + -sturbating (see etymology below) > elfsturbating
Latin masturbor (masturbate, debated etymology see below) + -tiō (nominalizer) > masturbātiō (masturbation) > French masturbation > masturbation > masturbating > -sturbating
Possible etymologies for 'masturbor':
manus (hand) + turbāre (to unsettle) > masturbor
manus (hand) + stuprāre (to defile (the self)) > masturbor
PIE *mosgʰos (marrow/brain) > *mostr̥gʰ- > masturbor (Calvert Watson tells us to compare “the symbolic autofellatio of Finn mac Cumaill's gnawing his thumb to the marrow"...apparently, sure I guess, whatever, why not, sounds fun)
Cognates for elf: Elbe (the European river), ऋभु (ṛbhú, artisan/craftsman, Sanksrit), ле́бедь (lébedʹ, swan, Russian), albino, Albania, Alba (Scotland, Scottish Gaelic), Albion, Alps, Albany, 𒀠𒉺𒀸 (alpas, cloud, Hittite), Alfred (and therefore Fred)