Where does “-dirlər” come from?

-dirlər (Azerbaijani) comes from Azerbaijani -dır, from Proto-Turkic *tüŕ-.

Ancestry of “-dirlər”, step by step

Step	Language	Word	Meaning
1	Azerbaijani	-dır	Form of -dir after the vowels A / I
2	Proto-Turkic	*tüŕ-	—