Larisa - From Russian name Larisa which is in use in Arm since XX c. It comes from Greek laris "pleasant", "fragrant". The others connect this name with Greek laros "sea-gull". The diminutive forms are Laris, Lara.
Pogosyan - Poghossian, Pogossyan, Poghosyan, Poghosian, Pogosyan, etc., is an Armenian surname.
The Western Armenian equivalent is Boghossyan.