The headword is the present indicative, third person singular, of the epic and Doric verb potini/somai (Attic pros-), I come to/go to; see generally LSJ s.v., Cunliffe s.v., and Buck, pp. 107-8. The entry is doubtless generated from the only attestation of the headword form: Homer, Iliad 9.381 (web address 1). There Achilles insists that he will not entertain Agamemnon's offer even should it amount to as much wealth as comes in to Orchomenos (an affluent ancient Mycenean Greek city in Boiotia, whose riches and greatness peaked about C13 BCE; Barrington Atlas map 57 grid A3; cf. omicron 674 and OCD(4) s.v. Orchomenus(1)); Hainsworth, pp. 112-3. NB: elsewhere -- in the scholia to the line (see next note), in quotations of it by Strabo and Pausanias, and in other lexica -- the form transmitted is potini/ssetai. On the question of single or double sigma, see LSJ s.v. ni/ssomai (web address 2).
[1] The gloss (that of the Homeric scholia: D scholia and scholia vetera) is the present indicative, third person singular, of the verb e)pe/rxomai, I come upon; see LSJ s.v.