The basis of the Italian lexicon is primarily Latin, with substrate features already existing in the languages spoken before the diverse population on the peninsula was Latinized, prior to the gradual conquest by the Romans, and with terms borrowed from Greek. In addition to the lexemes continued directly from Latin, Italian also shows a Germanic superstrate (Gothic, Lombard, Frankish) and an Arabic adstrate; many Germanisms, Arabisms and Hellenisms were borrowed in the Middle Ages. These were almost always in an adapted form, before the vernacular was given any recognition, and today form part of the “core vocabulary.” The Italian lexicon has also been supplemented by new learned Latin borrowings, exogenous lexemes, borrowings from the other languages with which Italian has been in contact, either directly or indirectly, and dialects (linguistic systems which developed independently of Tuscan/Florentine-based Italian). Similarly, there have been endogenous developments, mainly neologisms.
D'Achille, P. (2023). History of the Italian Lexicon. In Michele Loporcaro (a cura di), Oxford Encyclopedia of Romance Linguistics (pp. 1-27). Oxford : Oxford University Press [10.1093/acrefore/9780199384655.013.468].