Proto-IE: *bal-
Meaning: opening, hole, passage
Old Indian: bíla- n. `cave, hole, pit, opening', bílma- m. `slip, bit, chip; broken helmet'
Armenian: pelemi `höhle, grabe'
Celtic: MIr belachi `Kluft', Ir bealachi `Weg, Gebirgspass'
Russ. meaning: отверстие, проход