An Etymological Dictionary of the German Language/Forelle
Forelle, f., ‘trout,’ with a foreign accent, for the genuine dialectal (Franc.) fórelle, still existing; dimin. of an older Forene (whence *Forenle, Forelle); comp. MidHG. fórelle, fórle, forhen, forhe, f., ‘trout,’ OHG. forhana, f., ‘trout’; comp. also OLG. forna, furnie, AS. fôrne. Probably not from Föhre, OHG. foraha, ‘the fish living near firs, in the brooks of fir forests.’ It is probably connected with the Aryan adjs. in the cognate languages, meaning ‘spotted, speckled.’ Teut. forhana, from pre-Teut. prknâ; comp. Sans. pṛ́çni, ‘speckled,’ and Gr. περκνός, ‘livid, dusky’ (πέρκη, ‘perch’).