PS

*laṯaγ- - gum (SED I No. 182; Kogan 2011: 222)

Akkadian
lašḫu - gum (CAD L 108, AHw. 539)

with metathesis, note also *-γ- > -ḫ-.

Arabic
laṯaγat- - gum (BK 2 965)

Cf. a variant root laṯˁat-­ ‘the bottom of the lips on the inside, the part of the lips that touches the roots of the teeth’ [BK 2 965].