Have any linguists considered that if, early in the divergence of the PIE language family, if among some dialects a term like Ghabh was used to mean 'to receive', and in others 'to give', that term might translate as 'tribute'? If the speakers of some early PIE languages systematically gave, and others received, tribute, this might serve as a rough survey of systems of cultural and political dominance over a 3,000 year period of pre-/protoceltic history with no other contemporary records. In English we use 'give', 'grab', and 'gather' as successor terms, but few other modern languages are derived from as many mixed roots as English, and I gather most other modern languages of the PIE family use primarily one form 'give' or 'receive' after the Ghabh root.
Given the rate at which the PIE family spread across two continents with relatively little absorption of the pre-PIE languages on the way, speakers of early-PIE languages would seem to be anomalous of a reciprocal gift-giving society, as the simultaneous 'give/receive' meaning of ghabh seems to been interpreted by some to indicate.