Where does “chống lưng” come from?

chống lưng (Vietnamese) comes from Vietnamese lưng, from Proto-Vietic k-ləŋ, from Proto-Mon-Khmer t₁lan — python.

chống lưng (Vietnamese): to be supported or backed by a powerful entity (often from the shadow) so that one can get away with cheating or financial doping

Definitions

to be supported or backed by a powerful entity (often from the shadow) so that one can get away with cheating or financial doping

Ancestry of “chống lưng”, step by step

chống lưng traces back through two separate lines of ancestry.

via Vietnamese lưng

Step	Language	Word	Meaning
1	Vietnamese	lưng	back
2	Proto-Vietic	k-ləŋ	back
3	Proto-Mon-Khmer	t₁lan	python

via Vietnamese chống

Step	Language	Word	Meaning
1	Vietnamese	chống	to prop by using a stick-like object; to be...
2	Proto-Vietic	coːŋʔ	—

Every word from Proto-Mon-Khmer t₁lan →Every word from Proto-Vietic k-ləŋ →Every word from Vietnamese lưng →