Although the label of Proto-Mon-Khmer has mostly been abandoned or rejected, this reconstruction, which sourced from Shorto (2006)'s reconstruction for Proto-Mon-Khmer, currently does not have an appropriate Proto-Austroasiatic reconstruction. This reconstruction therefore should not be taken at face value as a state-of-the-art reconstruction for Proto-Austroasiatic, but instead ought to be treated as a valid cognate set.
Likely a nursery word, although its distribution throughout the various branches of Mon-Khmer suggests that it could be genuinely ancient.
Shorto (2006) and Blust & Trussel (ACD) relate Javaneseibu and Malayibu to a language, which may be of Austroasiatic descent, ancestral to Indonesia prior to the arrival of Western Malayo-Polynesian speakers.