The authors agree that the surname refers to a Lombard origin and that its central etymology is linked to a Germanic name related to the concept of "home". E. Rossoni specifies that this root is Aimo, from the Germanic haimi, meaning "homeland" or "home", and adds two alternative hypotheses: a derivation from the Hebrew name Caim (Cain) —referring to the word CAEM— and another from the Arabic qaim, with the sense of "the one who executes the will of God", the latter considered plausible at least for Sicily. For its part, Surnames in Italy links the surname to the Germanic name Haimo, noted as a diminutive of Haimrich.

Both sources agree that the Caimi were feudal lords of Turate, in the Como area. Rossoni places their presence among the most important families of Milan around 1277, while Surnames in Italy indicates that in 1377 they were registered among the families with the right to the election of canons of the Duomo, and that in 1623 the fief of Turate was granted to the judge Gaspare Caimi with the title of count. The main cluster of the surname is located in the Varese, Como and Milan areas, with extended presence in Piedmont, Liguria and Sicily. Rossoni also records the variant Caimmi, peculiar to the Falconara Marittima area, in the province of Ancona.