Where does “カンプチア” come from?

カンプチア (Japanese) comes from Khmer កម្ពុជា, from Pali kamboja, from Sanskrit काम्बोज, from Hindi कम्बोज — Kamboj.

Ancestry of “カンプチア”, step by step

Step	Language	Word	Meaning
1	Khmer	កម្ពុជា	—
2	Pali	kamboja	—
3	Sanskrit	काम्बोज	born in or coming from Kamboja; a native of...
4	Hindi	कम्बोज	Kamboj