Masqan
-nno/-o/-nno/-yyo - them (accusative pronominal suffix, 3 masc. pl.)
(Bulakh–Kogan 2013b:102)
-nno is the “light” form used with verbal forms of the suffix conjugation, -yyo is the “heavy” form. The “light” form used with verbal forms the prefix conjugation is -o (with the final consonant of the base doubled) / -nno. The “heavy” suffixes are used with 2 fem. sg, all the plural and impersonal verbal forms, the “light” suffixes are used in all the other cases (Bulakh–Kogan 2013b:105).