ˀiṯl - saliva, phlegm, spittle (DUL 125, Watson 2007: 79)

Even if this interpretation is maintained (which is far from obvious), there is hardly any need to postulate an Akkadian loanword in Ugaritic, all the more since none of the three ušultu words listed in CAD U 329 displays a suitable meaning (Kogan 2015: 360).