In English, the term Kalimantan refers to the Indonesian portion of the island of Borneo, while in Indonesian, the term “Kalimantan” refers to the whole island of Borneo.

The name Kalimantan which is often spelled Klemantan was derived from Sanskrit word: Kalamanthana which means “burning weather island”, or island with a very hot temperature to describe its hot and humid tropical climate. It consists of the two words kal[a] (time, season, period) and manthan[a] (boiling, churning, burning). The word Kalamanthana is spelled Kalmantan, and then the indigenous people fixed it into Klemantan.