The surname Macchi (spelled with a double c) is a distinct form from Machi (with a single c); although the two spellings may appear equivalent, the standard dictionaries of Italian surnames assign them different origins.

E. Rossoni identifies Macchi as a surname characteristic of northern Italy, concentrated especially in the areas of Varese and Novara, with a presence also in those of Pisa and Bologna. Rossoni reads its origin in several ways: it may derive from the Latin nomen Maccus, a stock character of Plautine comedy representing the guileless glutton; from the Celtic term makos, meaning "wood"; or, in some cases, from the reduction of old medieval compound names.

V. Blunda proposes a different etymology for the Sicilian occurrences of the surname, tracing it to the dialectal word màcchia, meaning "dense thicket" or "Mediterranean scrub" — the shrubby vegetation that typically covered uncultivated hillsides. As a surname, it could have originated as a microtoponym applied to someone who lived beside a stretch of such scrubland. This interpretation is supported by the source Surnames in Italy, which likewise treats the name as a topographic surname derived from macchia meaning "thicket" or "scrub," ultimately from the Latin macula, or alternatively as a habitational name from any of several places bearing that word, such as Macchia in the province of Trapani, Sicily.

By contrast, Machi — the single-c spelling — is a Sicilian surname documented mainly in the area of Palermo and is considered a separate name with its own distinct origin.