Where does “attiguus” come from?

attiguus (Latin) comes from Latin attingō, from Latin tangō, from Proto-Italic *tangō, from Proto-Indo-European denḱ- — to bite.

Ancestry of “attiguus”, step by step

Step	Language	Word	Meaning
1	Latin	attingō	—
2	Latin	tangō	—
3	Proto-Italic	*tangō	—
4	Proto-Indo-European	denḱ-	to bite

attiguus — Etymology, Origin & Word History | Etymology Explorer