The use of one verb (αματες/amatens) with the same value in the inscriptions I have already mentioned (see my posts Oenotrian amates. Part one / Oenotrian amates. Part two) and in Latin colloquial speech should not regarded as an isolated case, but rather as a widespread phenomenon, as is shown by the following examples.
The first example is a locution made up of an independent subjunctive plus derivative forms of *koisa-, which is attested both in the Paelignian official jargon (fesn upsaseter coisatens) and in Old Latin (for further details see Vittore Pisani, Manuale storico della lingua latina. IV. Le lingue dell’Italia antica oltre il latino, 2nd edition, 1964; Paolo Poccetti, Sul formulario dell’epigrafia ufficiale italica, in Athenaeum 61, 1983, pp. 178-198; Enrico Campanile, L’uso storico della linguistica italica. L’osco nel quadro della koiné mediterranea e della koiné italiana, in Latina & Italica, Paolo Poccetti ed., 2008, pp. 877-884).
The second example is a formula occurring in the Iguvine Tables (Va, 27), which includes an adverb (prufe) expressing the Atiedian Brothers’s approval of the ceremony they just performed and which, despite the obvious etymological connection of prufe with Latin probavit and probaverunt, should be regarded as an independent Umbrian creation rather than a borrowing in light of the existence of Oscan prúfatted (for further details see Enrico Campanile, I testi umbri minori, in Latina & Italica. Scritti minori sulle lingue dell’Italia antica II, Paolo Poccetti ed., 2008, pp. 799-810): Sve mestru karu fratru atiieřiu pure ulu benurent prusikurent rehte kuratu eru eřek prufe si (“If a majority of the Atiedian Brothers who have come there declare that it has been provided properly, it shall be well”).
The examples given above are likely to have arisen from a common, pre-documentary, source, which can be defined as “koiné italiana”, that is “Italian koine”.