Note: The semantic range of Old English fealu has long been a point of discussion, as the word is applied to entities (as the waves of the sea, faded flowers and the feet of a phoenix), notably in poetry, that cannot be easily labeled with a single color name in Modern English. It has been claimed that this and some other Old English color words (as well as their Germanic cognates) may describe degrees of brightness more than hue; for a critical discussion of the earlier literature see C.P. Biggam, "The ambiguity of brightness (with special reference to Old English) and a new model for color description in semantics," Robert E. MacLaury et al., editors, Anthropology of Colors, Benjamins, 2007, pp. 171-88. The modern word fallow is now rare outside of the collocation fallow deer. — Outside of the coherent Germanic and Balto-Slavic set exemplified by fallow, the Indo-European comparative data offer a good deal of semantic and formal diversity. As A. Nussbaum has pointed out ("The 'Saussure Effect' in Latin and Italic," A. Lubotsky, editor, Sound Law and Analogy, Rodopi, 1997, pp. 190-91), the words outside of Latin betray an original i-stem *pel-ei̯- and have the meaning "gray, lacking brightness." The Latin set exemplified by pallidus has a problematic a; a reconstruction *palu̯o- would allow Latin to be grouped with Germanic and Balto-Slavic, but the source of such a form is unclear.

Note: The Old English word is attested only as a gloss of the Latin word occa, and all occurrences of it appear to originate in a set of glosses to the tract De laude virginitatis, written by the seventh century Anglo-Saxon monk Aldhelm. Early on these glosses created scholarly confusion, as the usual meaning of the word occa in Medieval Latin was "harrow," which did not match the later history of the Old English word. A way out of this was shown by Johannes Hoops, who suggested that occa is more likely a variant of the Gaulish word olca "arable land" ("Felge und Falge: eine glossographische Untersuchungen zum Altertumskunde," Beiträge zur Geschichte der deutschen Sprache und Literatur, Band 27 [1912], pp. 313-24). The etymon *polḱ-eh₂ has been taken as a nominal derivative of a verb *pelḱ- "turn, bend" (hence Pokorny, Indogermanisches etymologisches Wörterbuch; Lloyd, Lühr et al., Etymologisches Wörterbuch des Althochdeutschen), alluding to the turning over of the soil in plowing. The word would hence be related to the etymon of felly entry 1, alleged to derive from the same verb.

Note: As suggested by the Oxford English Dictionary, third edition, the Middle English variants felyen, felowen, English dialect felly, would suggest the existence of a Class I weak verb *fielgan, which would seem to match Old High German felgen with the same sense.