Where does “inpugno” come from?

inpugno (Latin) comes from Latin impugno, from Latin in-, from Latin in, from Old Latin en, from Proto-Italic en, from Proto-Indo-European h₁én — in.

inpugno (Latin): Alternative form of impugnō

Definitions

Step	Language	Word	Meaning
1	Latin	impugno	I attack, fight against; I impugn, assail
2	Latin	in-	un-, non-, not; in, within, inside
3	Latin	in	in, at, on, upon, from; within, while in; into,...
4	Old Latin	en	in
5	Proto-Italic	en	in
6	Proto-Indo-European	h₁én	in