An Etymological Dictionary of the German Language/Annotated/Farn
Farn, masculine, neuter, ‘fern,’ from the equivalent Middle High German and Old High German varn, varm; corresponds to Dutch varenkruid, Anglo-Saxon fearn, English fern. The interchange of n and m in Old High German and Middle High German is due to the assimilation of the suffix na- to the initial labial; compare Old High German feim with Old Indian phêna, and Old High German bodam with Sanscrit budhna. Farn is wanting in Old Icelandic; yet compare Swedish dialectic fänne (Icelandic *ferne). The type is doubtlessly Aryan parna-, which is identical with Sanscrit parṇa, neuter, ‘wing, feather, foliage, leaf’; hence Farn is literally ‘feather-like leaf’ (Greek πτερίς, ‘fern,’ and πτερόν, ‘feather’). Probably allied also to Lithuanian papartis, Russian paporotĭ (Old Slovenian *papratĭ), ‘fern.’