Where does “majakъ” come from?

majakъ (Slavic) comes from Proto-Slavic majati, from Proto-Balto-Slavic māˀ-.

Ancestry of “majakъ”, step by step

Step	Language	Word	Meaning
1	Proto-Slavic	majati	to beckon; to wave; to detain, to dawdle
2	Proto-Balto-Slavic	māˀ-	—