This one is the one that caught my attention first - it's a Yiddish lullaby, "Oyfn Veg Shteyt a Boym," by Itzik Manger (1901-1969) - lyrics at Zemerl.
The title of this particular video is "Kolibyel'niye mira. Idish" I know the third word is Yiddish, but I can't figure out what "Kolibyel'niye mira" means.