-kum - your; you (genitive and accusative pronominal suffix, 2 masc. pl.) (Bulakh–Kogan 2013b:101)

Just as the singular forms, the plural of the pronominal suffix of the 2nd person is based on the element k- with the extension -m- or -n- combined with more or less expressed vocalic oppositions (Kogan 2009:69). The character of consonantal and vocalic oppositions in individual languages generally corresponds to the nominative forms.