Where does “запу́гивать” come from?

запу́гивать (Russian) comes from Russian запуга́ть, from Russian за́-, from Proto-Slavic za- — for.

Ancestry of “запу́гивать”, step by step

Step	Language	Word	Meaning
1	Russian	запуга́ть	—
2	Russian	за́-	—
3	Proto-Slavic	za-	for

запу́гивать — Etymology, Origin & Word History | Etymology Explorer