Lhokpu is spoken by the Lhop—a Dzongkha term meaning "Southerners"—, who "represent the aboriginal [gdung] Dung population of western Bhutan [....] Lhokpu is more closely related to the Eastern Kiranti languages of Nepal such as Lohorung or Limbu than to the Lepcha, and, in linguistic terms, Lhokpu seems to be the substrate language for Dzongkha in western Bhutan.".
^Nordhoff, Sebastian; Hammarström, Harald; Forkel, Robert; Haspelmath, Martin, eds. (2013). "Lhokpu". Glottolog 2.2. Leipzig: Max Planck Institute for Evolutionary Anthropology.
^Driem, George van (2001). Languages of the Himalayas : an ethnolinguistic handbook of the greater Himalayan Region : containing an introduction to the symbiotic theory of language. Leiden: Brill. ISBN978-9004103900.
^Driem, George van (1998). Dzongkha = rdoṅ-kha. Leiden: Research School, CNWS. p. 29. ISBN978-9057890024.