The habit of treating the two-word phrase e)pi\ ma=llon as one word seems to be largely a Byzantine phenomenon. Yet see the next entry, epsilon 2455, where an instance of it is ascribed to the 3rd-century CE historian Dexippos of Athens. Of course the issue of whether any individual author conceived of it as a single word is easily obscured, beyond recovery, in the process of textual transmission, and it is rarely clear why modern editors choose one version over the other. See next note.
[1] Aelian fr. 252 Hercher, 250a Domingo-Forasté; quoted at greater length at epsilon 1555, where Adler accepts Kuster's questionable emendation of the e)pi\ ma=llon of the mss to e)/ti ma=llon ('still more'). See further comments at epsilon 1555.