Where does “тꙑлъ” come from?

тꙑлъ (Old East Slavic) comes from Proto-Slavic tylъ — back of the neck, nape.

Ancestry of “тꙑлъ”, step by step

Step	Language	Word	Meaning
1	Proto-Slavic	tylъ	back of the neck, nape

тꙑлъ — Etymology, Origin & Word History | Etymology Explorer