The name "del Cacco" may refer to the Roman deity Cacus, or more likely to a statue of the dog-headed (baboon, actually) ancient Egyptian god Thoth[1] (from the temple of the ancient Egyptian deities Isis and Serapis, the Iseum Campense, built in 43 BC, on whose ruins the church was originally built and twelve columns from which were re-used in the church's nave), misunderstood as a monkey or "Macaco" (later corrupted to Cacco).

[7] Paolo Marucelli (1594–1649) designed the church's travertine portal, flanked by pilasters and surmounted by a triangular pediment, and the plate above it reads: D. STEPH.

On the sides of the portal were once located the two basalt lions, coming from the "Temple of Isis", and subsequently placed by Michelangelo at the base of the Cordonata.

Restorations and renovations occurred in 1607 (gutting the apse), c.1640 (giving the church its current baroque appearance,[3] with a simple 2 storey façade, probably by Antonio Canziani).

[8] In the mid-19th century, the floor was re-laid with marble salvaged from the burnt-out San Paolo fuori le Mura.