'stipend' : How did 'a tree trunk' evolve to mean 'payment, gift'?

Question

stipend (n.)    early 15c., "periodical payment; soldier's pay," from Latin stipendium "tax, impost, tribute," in military use "pay, salary," from stips "alms, small payment, contribution of money, gift" + pendere "weigh" (see pendant). According to Klein's sources, the first element is related to Latin stipes "log, stock, trunk of a tree" (see stipe). As a verb from late 15c.

I fail to imagine how stipes evolved into stips. Would someone please advise?

I heed the Etymological Fallacy. But what are some right ways of interpreting this etymology, to make it feel reasonable and intuitive?

Answer 1

Once again, Varro has an explanation to propose. For what it's worth. In Lingua Latina Book 5, 182. (Book 5 has a lot of etymologies for many words related to money).

tl;dr According to Varro, these coins of little value were commonly offered to the Gods in alms boxes (mites) called stirps 'trunks' (supposedly carved out of a trunk - see trunk as coffer/chest and then trunk/boot of a car).
Although this etymology seems to rely on the similarity between stirps and stips, please note that:

1. The French word for such a mite in churches is still tronc.
2. Stirpe in Present Day Italian still means offspring => race => pedigree
3. One of the meanings of stips, stipis is precisely that of alms.

182. Hoc ipsum stipendium a stipe dictum, quod aes quoque stipem dicebant: nam quod asses librae1 pondo erant, qui acceperant maiorem numerum non in arca ponebant, sed in aliqua cella stipabant, id est componebant, quo minus loci occuparet; ab stipando stipem dicere coeperunt. Stips ab στοιβή fortasse, Graeco verbo. Id apparet, quod ut tum institutum etiam nunc diis cum thesauris asses dant stipem dicunt, et qui pecuniam alligat, stipulari et restipulari. Militis stipendia ideo, quod eam stipem pendebant; ab eo etiam Ennius scribit:

                Poeni stipendia pendunt.

Translation from Loeb 333:

182. This very word stipendium 'stipend' is said from stips 'coin,' because they also called an aes 'copper coin' a stips; for because the asses were a pound each in weight, those who had received an unusual number of them did not put them in a strong-box, but stipabant 'packed,' that is componebant 'stored,' them away in some chamber, that they might take up less space; they started the use of the word stips from stipare 'to pack.' Stips is perhaps from the Greek word στοιβή heap.' This is clear, because, as was then started, so even now they speak of a stips when they give money to the temple treasuries for the gods, and those who make a contract about money are said to stipulari 'stipulate' and restipulari 'make counter-stipulations.' Therefore the soldier's stipendia 'stipends,' because they pendebant 'weighed' the stips; from this moreover Ennius writes:

                The Phoenicians pay out the stipends.

For good measure, I'm including the French translation which, I find clearer:

182. Stipendium (solde) vient de stips, nom qu'on donnait aussi à la monnaie de cuivre. Comme l'as pesait une livre, ceux qui en avalent reçu une grande quantité déposaient leur argent, non dans une cassette, mais dans quelque lieu convenable, où ils le rangeaient et l'entassaient, pour qu'il occupât moins de place; et de stipare on a fait stips. On pourrait voir aussi l'origine de stips dans le mot grec στοιβή, qui a le même sens que stipatio. Ce qui autorise cette étymologie, c'est qu'on appelle stips l'offrande d'argent que, suivant l'usage antique, on dépose dans le tronc des temples, et que stipulari et restipulari se disent de ceux qui s'engagent à payer une somme. Stipendium est composé de stips et de pendere (peser, payer). On lit dans Ennius :

                Poeni stipendia pendunt