SPQR

SPQR is an initialism of a Latin phrase ("The Roman Senate and People", or more freely as "The Senate and People of Rome"; Classical Latin: [sɛˈnaː.tʊs pɔpʊˈlʊs.kᶣɛ roːˈmaː.nʊs]), referring to the government of the ancient Roman Republic, and used as an official emblem of the modern-day comune (municipality) of Rome. It appears on Roman currency, at the end of documents made public by inscription in stone or metal, in dedications of monuments and public works, and was emblazoned on the vexilloids of the Roman legions.

The phrase commonly appears in Roman political, legal and historical literature, including the speeches of Cicero and Ab Urbe Condita Libri ("Books from the Founding of the City") of Livy.

SPQR: Senātus Populusque Rōmānus. In Latin, is a nominative singular noun meaning "Senate". is compounded from the nominative noun , "the People", and , an enclitic particle meaning "and" which connects the two nominative nouns. The last word, ("") is an adjective modifying the whole of : the "Roman Senate and People", taken as a whole.

Thus, the sentence is translated literally as "The Roman Senate and People", or more freely as "The Senate and People of Rome".

The title's date of establishment is unknown, but it first appears in inscriptions of the Late Republic, from c. 80 BC onwards. Previously, the official name of the Roman state, as evidenced on coins, was simply ROMA. The abbreviation last appears on coins of Constantine the Great (ruled AD 312-337), the first Christian Roman emperor.

...
Wikipedia