borrowed from Latin, combining form from ambō, ambae "two of a pair, both," going back to Indo-European *h2(e)nt-bhoh1 (whence also Germanic *bai "both," Greek ámphō, Old Church Slavic oba, obě, Lithuanian abù, abì, Tocharian A āmpi, Tocharian B antapi, āntpi, Sanskrit ubháu, ubhé, Old Avestan uba-, Young Avestan uua-), probably from *h2ent- "front, face" + -bhoh1, dual ending analogically imposed on an oblique case ending *-bh- — more at ante-
Note: Outcomes of the Indo-European etymon are irregular: the nasal component has been lost in Balto-Slavic and Indo-Iranian, and the Germanic outcome has lost the initial syllable entirely—for details of the latter see both entry 3. The -t- of the initial element *h2(e)nt- is preserved only in Tocharian B if this etymology is correct. For the original proposal see Jay Jasanoff, "Gr. Ἄμφω, lat. ambō, et le mot indo-européen pour 'l'un et l'autre'," Bulletin de la Société de Linguistique de Paris, tome 71 (1976), fascicule 1, pp. 123-31. — Latin ambi- in the sense "both" was a late innovation, apparently not attested before apuleius, who uses the word ambifāriam "in a way that places an opponent in a dilemma," based on bifāriam "in two places/ways." Words such as ambidens "having teeth on both upper and lower jaws," cited by the grammarian Sextus Pompeius Festus, are probably artificial creations. In part ambi- is modeled on Greek amphi- "on both sides" (see amphi-), in part it is based on a reinterpretation of the prefix amb- "around, circling" (see ambient entry 1)