People since olden times began to be settled on both banks of Psla. Already in II - VI centuries of new era the Slavic tribes lived here, bits and pieces of their settlements and burial grounds found out in south-west part of city, outside Pavlova. The name a city got from the small rivers Bag and Bag, that washed him both-side. Legend reached to our days, that in place, where Sumy stand, game-bags were found.