Mehri

sār - behind; back, backwards (ML 351)

Likely related with a meaning shift.

Proto-MSA
*sar - behind (Kogan 2015:569)
The origin of Proto-MSA *sar ‘behind’ is uncertain. Contra W. Leslau and M. Bittner (1914:15), any connection with PS *ˀaṯar- ‘trace’ can be safely excluded for phonological reasons. Quite far-fetched is the comparison between the MSA terms and Arb. sarīr- ‘the part where the head rests upon the neck’ (Lane 1339), sarāt- ‘back’ (ibid. 1353), Amh. säräsär ‘vertebra, spinal cord’ (AED 487) suggested in SED I No. 253. Shall one rather compare Hbr. swr ‘to turn aside’ (HALOT 748), assuming a semantic development from the more original meaning “to turn back”? (Kogan 2015:569)