Pronounced hu lang (falling tone) in Guangyun (Guangyun), with a similar sound to "kang." Yipian (Yipian) explains it as the gap between muscles. Additionally, Guangyun (Guangyun) records "lang pu," which is the name of a kingdom of southern barbarians. Zuo Si's "Wu Du Fu" (Wu Du Fu) contains the sentence "wu hu lang pu." [Annotation] Yi Wu Zhi (Yi Wu Zhi) states: Lang pu people can discern the quality of gold by smelling it with their noses at night.