Proto-Austroasiatic language
Proto-Austroasiatic is the reconstructed ancestor of the Austroasiatic languages. Proto-Mon–Khmer (i.e., all Austroasiatic branches except for Munda) has been reconstructed in Harry L. Shorto's Mon–Khmer Comparative Dictionary, while a new Proto-Austroasiatic reconstruction is currently being undertaken by Paul Sidwell.
Source: Wikipedia — Proto-Austroasiatic language (CC BY-SA 4.0)