What is "osam"

The Òsam is a river in northern Bulgaria. Its drainage basin is in between that of the river Vit to the west and the Yantra system to the east. The river has two main tributaries in its upper course: the Black Osam takes its source from the foot of Levski Peak in the Balkan Mountains, at an altitude of , while the White Osam has its source on the northern slopes of the Kozya Stena peak. In Troyan, the black and white Osam join. It runs north towards Lovech, then north-east until Letnitsa and Levski, where it turns north-west until it flows into the river Danube 5 km west of the town of Nikopol. The ancient name of the river was Assamus.