Samuel Ball Platner, A Topographical Dictionary of Ancient Rome, London: Oxford University Press, 1929.

Esquiliae: * (A) The earlier general name for the Mons Oppius and Mons Cispius (q.v.) the two projections from the hight ground on the east of the city afterwards known as the mons Esquilinus. Esquiliae is in form a place-name and was so treated grammatically (Cic. de nat. deor. iii. 63; de legg. ii. 28; cf Madvig, Kl. shrift. 299). It is derived from ex-colo (Walde, Etym. Worterb. s.v.; cf. inquilinus, and for fanciful etymologies, Varro, LL v. 49; Ov. Fast. iii. 245), and meant 'an outside settlemeent,; that is, the settlment on the Oppius and Cispius when that district was still beyond the limits of the Palatine city. Von Duhn's explanation (Italische Graberkunde i. 468 sqq.) of Esquiliae as 'Nicht-Wohngebiet,' i.e. necropolis, is tempting. He points out that it was devoted to this use as early as the time of the Kings, though (p 434) he also notes that very few cremation tombs have actually been found- so far as we can gather from the insufficient reports that are the only sources of our information. In point of time its use is of course later than that of the necropolis of the forum, belonging as it does to the period after the enlargement of the Septimontium into the city of the four regions. Regio Esquilina was the second in the City of the Four Regions (Varro, LL v. 49-50), and comprised the Oppius, cispius, Subura, and Argiletum. Its eastern limit must have been the ancient necropolis which began near the present S. Martino ai Monti (KH i.). After the Servian wall was built, the eastern limit of the region probably coincided with the wall, and the adjacent district beyond was organised as the Pagus Montanus (q.v.). At the end of the republic the Puticuli (q.v.) were ultra Esquilias (Varro, LL v. 25). This region was well wooded at first, as is shown by the several luci (Fagutalis, Mefitis, Esquilinus, Lucinae) within its limits.

Esquiliae was the term in general use in the earlier period, at least in literature. Mons Esquilinus is found only once in Cicero (de rep. ii. II) and for the first time, and is not used at all by Livy, Tacitus, Pliny, Suetonius, or Martial, but it was adopted by Greek writers, and became common after the first century (RE vi. 683).

(B) The name of the fifth region of Augustus' city, which was entirely outside the line of the Servian wall, and therefore contained no part of the original Esquiliae. Of the republican Esquiliae, the Oppius fell in the third and the Cispius in the fourth region. It is not possible to determine the limits of this region in the Augustan period with certainty at all points, but in the fourth century its western boundary coincided with the Servian agger and wall from the porta Viminalis to a point just south of the temple of Isis, and from there appears to have run straight to the porta Asinaria. Thence it followed the Aurelian wall to the castra Praetoria, except between the amphitheatrum Castrense and the aqua Claudia, wher it curved out some 200 meters. Its northern boundary was the street between the porta Viminals and the gate in the Aurelian wall south of the castra Praetoria. Of this area most of that part north of the via Tiburtina vetus was probably not included in Region V until the time of Vespasian (Mitt. 1897, 150-151). A large section of the region was occupied by parks, horti (q.v.), and there were numerous distributing stations of the seven aqueducts that entered the city at the porta Praenestina. For this reason the Esquiliae are called aquosae (Prop. iv. 8. 1, 58).