Possibly but not necessarily an Arabism; cf. TNA in the comments below

    MHR and JIB räḥm are quite likely Arabisms, while forms in mǝ- are shaped after a derived pattern and look genuine.

    There is a derived meaning 'compassion, pity, mercy, kindness' and a corresponding verb to be reconstructed for as early as PSEM: AKK rēmu, rīmu 'Erbarmen, Mitleid' OB on [AHw 970]; UGR rḥm 'mitleidsvoll, liebevoll sein' [Aist 291]; HBR rḥm (ḳal, piʕ) 'to love, to meet someone with love, to take pity on someone' [KB 1217], raḥămīm 'a feeling of love, loving sensation, mercy' [ibid. 1218] (with an unusual vocalism, instead of *rǝḥāmīm); ARM: BIB raḥămīn 'Erbarmen' [KB deutsch 1781], MND RHM 'to love, to have pity' [DM 426]; ARB rḥm 'être compatissant, avoir pitié de quelqu'un' [BK 1 838]; SAB rḥm 'to be merciful' [SD 116]; MSA: MHR rǝḥām 'to be kind to so.' [JM 321], HRS reḥām 'to pity' [JH 103], JIB raḥám 'to be kind' [JJ 210]. Note that in ETH only a variant root *mḥr with metathesis is attested (HAR raḥmät 'mercy, compassion' [LHar 134] and related forms are Arabisms): GEZ mḥr 'to have compassion' [LGz 336], TGR mäḥarä 'to have pity' [LH 111], TNA mäḥarä 'avere pietà' [Bass 78], AMH marä 'to pardon, forgive, to have mercy' [K 171], EAST: WOL marä, SEL ZWY mārä 'to forgive, pardon' [LGur 417].

    Rather of an areal usage is another derived meaning, 'slavegirl', attested in UGR and CAN languages only: UGR rḥm 'Maid' [Aist 291], MOAB rḥm 'kriegsgefangene Konkubine' [Segert 266], HBR räḥäm 'slavegirl' (in Ju 5:30) [KB 1217].

    [Fron 47] (*raḥm- /ARB,SYR,HBR,UGR rḥm 'ragazza' AKK/); [Holma 104]: AKK, ARB, HBR, ARM; [KB 1217]: HBR, ARM, AKK, UGR, ARB