An Etymological Dictionary of the German Language/Annotated/Fittich
Fittich, masculine, from the equivalent Middle High German vittich, vëttach, masculine, neuter, vëttache, feminine, masculine, ‘wing, pinion,’ Old High German fëtah, older fëthdhah, masculine; in meaning a collective of Feder; compare Old Saxon fëtherac, Old High German fëderah, Middle High German fëdrach, ‘wing’; the formation of Old High German fëthdhah is not clear; was the Gothic form *fiþþaks? The dentals are obscure, yet the word is undoubtedly related to Feder.