Virgil says of Romulus, “Mavortia condet moenia, Romanosque suo de nomine dicet” (AEneid, i. 276). The words of the Sibyl, quoted by Servius, are Romulus is a diminutive or word of endearment for Romus.
The etymology of Rome from Roma (mother of Romulus and Remus), or from Romulus, the legendary founder of the city, or from ruma (a dug), in allusion to the fable of a wolf suckling the outcast children, is not tenable. Niebuhr derives it from the Greek word rhoma (strength), a suggestion confirmed by its other name Valentia, from valens (strong). Michelet prefers Rumo, the ancient name of the river Tiber.
Founders of Rome. (1) Romulus, the legendary founder, B.C. 752; (2) Camillus was termed the Second Romulus, for saving Rome from the Gauls, B.C. 365; (3) Caius Marius was called the Third Romulus, for saving Rome from the Teutones and Cimbri, B.C. 101.
From Rome to May. A bantering expression, equivalent to the following:- “From April to the foot of Westminster Bridge;” “Inter pascha Rennesque feror” (Reinardus, ii. 690); “Inter Cluniacum et Sancti festa Johannis obit” (Reinardus, iv. 972); “Celasest passé entre Maubeuge et la Pentecóte.”
'Tis ill sitting at Rome and striving with the Pope. Never tread on a man's corns. “Never wear a brown hat in Friesland” (q.v.).
“Mr. Harrison the steward, and Gudyell the butler, are no very fond o'us, and it's ill sitting at Rome and striving with the pope, sae I thought it best to flit before ill came.” —SirW.Scott: Old Mortality, chap. viii.
Oh, that all Rome had but one head, that I might strike it off at a blow! Caligula, the Roman emperor, is said to have uttered this amiable sentiment.
When you go to Rome, do as Rome does i.e. conform to the manners and customs of those amongst whom you live, and don't wear a brown hat in Friesland. St. Monica and her son St. Augustine, said to St. Ambrose: At Rome they fast on Saturday, but not so at Milan; which practice ought to be observed? To which St. Ambrose replied, “When I am at Milan, I do as they do at Milan; but when I go to Rome, I do as Rome does.” (Epistle xxxvi.) Compare 2 Kings v. 18, 19.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894