Where does “พนมเปญ” come from?

พนมเปญ (Thai) comes from Khmer ភ្នំពេញ, from Khmer ភ្នំ, from Proto-Mon-Khmer bn₂uum — hill.

Ancestry of “พนมเปญ”, step by step

StepLanguageWordMeaning
1Khmerភ្នំពេញ—
2Khmerភ្នំhill, mountain
3Proto-Mon-Khmerbn₂uumhill
Every word from Proto-Mon-Khmer bn₂uum →Every word from Khmer ភ្នំ →Every word from Khmer ភ្នំពេញ →