In the Vienna Corpus the concept “big” is expressed by the suppletive combination of eb for the masculine vs. am for the feminine. Numerous illustrations can be found in D. Müller’s special note on the subject (Müller 1909:347-351), such as bilâd ʔéeb/ḥadíboh ʔam ‘die große Stadt’. In the dialect of the Da’rho tribe, upon which CSOL I is based, this usage is obsolete: the adjectives am and eb are restricted to the comparative expressions like mḥámmad eb ʕan áḥmad ‘Muhammed is bigger than Ahmad’ or fáṭma am ʕan sál’wa ‘Fatima is bigger than Selwa’, but still current in their original basic function in the Western Soqotri dialects, according to a personal communication from Miranda Morris.
(Kogan 2015: 487)
The origin of em- is uncertain. Perhaps, it shall be identified with the North Yemeni form of the definite article (see Behnstedt 33).