Though the headword verb is presented here (and in some other lexica) in the paradigmatic first person singular, present indicative, its only appearance outside lexica etc. is in Homer, Iliad 10.65 (web address 1), where it is in the first person plural, aorist subjunctive active a)brota/comen (in the construction after a command + mh/: Chantraine, Grammaire homérique, vol. 2, pp. 208-209, paras. 307-308). Agamemnon tells Menelaus to stay where he is, 'in case we somehow miss each other on the way, for there are many paths in the camp').
The verb is formed with the deverbative suffix -a/zw from the Aeolic aorist a)/broton, h)/mbroton (eta 286) of a(marta/nw, i.e. the verb in the present gloss; cf. alpha 1495, alpha 1499, and H.J. Mette in Lexikon des frühgriechischen Epos 1.81-19, citing Risch and Schwyzer.
The glossing derives from Apollonius the Sophist [Apollonius(11) in OCD(4)], Homeric Lexicon 3.1 (= Hesychius alpha205, and cf. Etymologicum Gudianum 3.25ff., Eustathius Commentary on Iliad 10.65), probably following Aristarchus, on Homer's plural.