Where does “*-anъ” come from?

*-anъ (Proto-Slavic) comes from Proto-Slavic -ěnъ — Forming adjectives meaning 'made of '; -en.

Ancestry of “*-anъ”, step by step

Step	Language	Word	Meaning
1	Proto-Slavic	-ěnъ	Forming adjectives meaning 'made of '; -en

*-anъ — Etymology, Origin & Word History | Etymology Explorer