Where does “sappa” come from?

sappa (Pali) comes from Sanskrit सर्प, from Sanskrit सृप्, from Proto-Indo-European serp- — to creep, crawl.

sappa (Pali): snake

Definitions

Step	Language	Word	Meaning
1	Sanskrit	सर्प	creeping, crawling, stealing along; a snake,...
2	Sanskrit	सृप्	—
3	Proto-Indo-European	serp-	to creep, crawl

sappa — Etymology, Origin & Word History | Etymology Explorer