An Etymological Dictionary of the German Language/Annotated/Haar
Haar (1.), masculine, ‘flax,’ from the equivalent Middle High German har, Old High German haro (genitive Middle High German and Old High German harwes), masculine; Gothic *harwa- (genitive *harwis) is also implied by Old Icelandic hǫrr (dative hǫrve), masculine, ‘flax.’ As to its connection with Haar (2.) see the latter. Perhaps the word is most closely related to English hards (‘refuse of flax, tow’). See Hede.
Haar (2.), neuter, ‘hair,’ from the equivalent Middle High German and Old High German hâr, neuter; compare the corresponding Old Icelandic hâr, neuter, Anglo-Saxon hœ̂r, neuter, English hair, Dutch haar; a common Teutonic word (in Gothic, however, tagl and skuft). The following Teutonic words are also primitively allied — Old Icelandic haddr and Anglo-Saxon heord, ‘hair’ (Gothic *hazda), as well as Irish cass, ‘curled hair.’ In the non-Teutonic languages compare Old Slovenian kosmŭ, masculine, kosa (Lithuanian kasa), feminine, ‘hair,’ and probably also Old Slovenian čésati, ‘to comb,’ Latin carere, ‘to card wool.’ The more definite relations in sound existing between these words are difficult to determine (compare also Greek κόμη, Latin coma?). On the other hand, there is no phonetic difficulty in connecting the Teutonic *hera-, ‘hair,’ with harwa-, deduced under Haar (1.); the mere possibility is, however, all that can be maintained. Compare also Locke and kraus. — An old derivative of Haar, Anglo-Saxon hœ̂re, Old High German hârâ, hârrâ, feminine, ‘hair shirt, coarse garment,’ found its way into Romance (French haire).