Akkadian

balāṣu - to stare, to stare with wide open eyes (CAD B 44, AHw. 98)

Cf. balṣu, palṣu 'staring' (CAD); in b/palsa īni(m) 'glotzäugig' (CAD B 45, AHw. 100).
WS borrowing?

PWS
*blṣ - to glow, to shine, to appear (EDA B 40)