See also tabku 'stores of grain' (AHw 1295, CAD T 28), tibku 'outpouring, deposit' (AHw 1354, CAD T 379), tubku 'heap (?)' (AHw 1365, CAD T 446), tabākattam 'mng. uncert.' (AHw 1295, CAD T 1), tubukkû 'heaped-up grain' (AHw 1365, CAD T 448), tubukku 'stored' (AHw 1365, CAD T 445), natbāku/natbaku 'granary; libation; ravine; layer of bricks' (AHw 766, CAD N2 118), natbāktu/natbaktu 'sluice (?)' (AHw 766, CAD N2 117), tatbīku 'coating, plating' (AHw 1340, CAD T 299). In spite of several attempts, no reliable etymology has been found. CAD T 10 may be right to surmise that “in view of the wide range of meanings of the verb, it is probable that two or even three verbs coalesced in tabāku”. See the discussion of some suggestions in EDA II.
No reliable etymology can be proposed. Hardly any connection to PWS *bayna.
Attested in the newly published NB fragment of the third tablet of Hh. Any reasonable semantic connection to tabāku pending, the substantive has been provisionally separated from it, even if no alternative etymology is at hand.
G stem attested only as infinitive.