probably an early WS loanword (Kogan2008b:105 and 110, with references)
Var. bašKiKītu, ašKiKītu, mašKiKītu.
No etymology can be suggested. The spelling alternation b-/m-/Ø- may suggest *w in the prototype.
Cf. Kogan 2015:571.
Likely from ana šumi (lit. 'for the name', see GAG 207, CDG 43). See also the expression ana šumi 'because of, as for' (CAD Š₃ 294, AHw. 295), in which both lexemes are used separately.
Var. ḫašû, ušû