Many facts show that toponyms can portray the closeness of humans to the surrounding nature. In this context, the relationship between humans and the surrounding nature can also form local knowledge. This research aims to reveal the classification and function of the lexicon in local knowledge-based toponyms in the western Lembang Fault area. This research used the theoretical approach of anthropological linguistics. In addition, this study also used three data collection methods, including participant observation method, interview method, and documentation method. The results of this study show that five toponyms are included in the physical aspect, which combines hydrological and biological characteristics. In addition, there are five toponyms included in the physical aspects that have a combination of geomorphological characteristics and biological characteristics. Furthermore, three toponyms are included in the social aspect, characterized by circumstances. Finally, two toponyms, which have religious or mythological characteristics, are included in the cultural aspect. In addition, the results of this study also show the function of toponyms in the western Lembang Fault area. This function captures the local knowledge of Sundanese people about the existence of a vertical relationship dimension between humans and God and a horizontal relationship dimension between humans and nature.