The headword is the aorist subjunctive active, third person plural, of the verb o)fe/llw, which is an epic, Aeolic, and archaic form of o)fei/lw (I ought, owe, exalt, have to account, am obliged to); see generally LSJ s.v., and cf. omega 268, omega 273, omega 994, and omega 995. It is extracted from Homer, Iliad 1.510 (web address 1), its first attestation, where Thetis asks Zeus to ensure that the Achaeans 'advance' (= increase) her son Achilles in honor; see Cunliffe, p. 307.
[1] The gloss, which follows the scholion (= D scholia) to the aforementioned Homeric passage, is the aorist subjunctive active, third person plural, of the verb au)ca/nw, I increase, augment, gratify; see LSJ s.v., Apion and Hesychius s.v. o)fe/llein, ps.-Herodian 104, and Etymologicum Magnum 643.55. Adler also notes that the lemma is identically glossed at Lexicon Ambrosianum 676.