The Esquiline hill is actually a combination of 3 other hills called Cispius, Oppius and Fagutalis. Oppius is most commonly referred to also in common speech so that “Colle Esquilino” and “Colle Oppio” are often interchangeable.
This hill or set of hills was included in the city of Rome by the later 6th King of Rome Servius Tullius. The name “Esquiline” is of unclear provenance, possibly linked to “Exquilini” meaning outsiders.
In ancient times the Esquiline hill was a relatively suburban area with respect to the historic centre of the city at the Palatine, Capitoline and Forum areas. Rich villas and sumptuous gardens were built there by some of the city’s richest individuals.