The etymology of the river's name is derived from a pre-Slavic form Alb that underwent linguistic metathesis within Slavic giving the final form as Lab.

[2] Many scholars take the hydronym Lab as ancient and derive it from an alb-, from which lab-, alp- could come.

[2] Near its origin are the remains of one of the medieval palaces of Serbian King Milutin (1282-1321) called Vrhlab.

[3][4] Ottoman writer Evliya Celebi mentioned the Llapi river as having "its source in Albania" and joining other rivers before flowing into the Danube, during one of his travels to Kosovo in the 1660s.

[6] The width of the river changes due to the dynamics of rivers, it is around 9–12 meters at the hydrometric point in Lluzhan and it has a depth up to 1.2 m (3.9 ft), that varies based on the season and the location.