Proto-MSA

*ṣlp - to shine, to be bright (Kogan 2015:570)

The origin is unknown. (Kogan 2015:570)

Mehri
ṣəlūf - to be visible from far away (ML 362)
Jibbali
ṣɔ́lɔ́f - to appear quickly and vanish; to be seen from far away; to dazzle (JL 239)