A WS lexeme with the lateral sibilant *ŝ, appropriately rendered with the combination -lt- in the cuneiform (Jursa 2009, 156f., Kogan 2011, 78). Cf. Cf. Pho. bšm “perfume, spices” (DNWSI 203), Hbr. bōŝäm, *bäŝäm, *bāŝām “balsam tree, balsam oil” (HALOT 163), etc.
In Oelsner 2005-2006, 121 and Horowitz 2014, 234, fn. 1584 it is proposed to derive bālu from baʾālu “to be large” (KP002). This interpretation, although semantically plausible, is hampered by the absence of the “strong aleph” in bālu (one would expect *baʾlu) (EDA B 041a).