An Etymological Dictionary of the German Language/Farn
Farn, m., n., ‘fern,’ from the equiv. MidHG. and OHG. varn, varm; corresponds to Du. varenkruid, AS. fearn, E. fern. The interchange of n and m in OHG. and MidHG. is due to the assimilation of the suffix na- to the initial labial; comp. OHG. feim with OInd. phêna, and OHG. bodam with Sans. budhna. Farn is wanting in OIc.; yet comp. Swed. dial. fänne (Ic. *ferne). The type is doubtlessly Aryan parna-, which is identical with Sans. parṇa, n., ‘wing, feather, foliage, leaf’; hence Farn is lit. ‘feather-like leaf’ (Gr. πτερίς, ‘fern,’ and πτερόν, ‘feather’). Probably allied also to Lith. papartis, Russ. paporotĭ (OSlov. *papratĭ), ‘fern.’