The meaning is hardly connected to that of PCS
*rgm ‘to stone’.
In Soq. rígɛm ‘to be stoned’ and régom ‘to cover, to protect’ to be treated as different (homonymous) roots, as actually done by Leslau in LS 394. At the same time, it is noteworthy that one of the prominent applications of rgm in Jibbali is connected with covering a dead body with stones. The same semantic nuance is attested in Arabic:
raǯam- ‘stones that are placed upon a grave,’
rǯm (II) ‘to place a stone on one’s grave’. It is likely that the meaning “to cover with stones” in Arabic represents a secondary development from “to stone (as punishment),” which, in its turn, influenced Jib. rgm ‘to cover,’ originally unconnected to *rgm ‘to stone’
(Kogan 2015: 217-218)