Watching a video of a reconstruction of ancient Rome brought my attention to "Fausta Felicitas."
In addition to Virgil's "Felix quit potuit...." passage I presume that the Romans in general would have connected the word "Felicitas" to the happiness described by Epicurus and the other philosophers. Presumably there were Latin translations of the letter to Menoeceus and if so would not felicitas have been the most likely translations of the happiness Epicurus refers to when he said that if we have it we have everything(?)
Felicitas had a temple in Rome as early as the mid-2nd century BC, and during the Republican era was honored at two official festivals of Roman state religion, on July 1 in conjunction with Juno and October 9 as Fausta Felicitas. Felicitas continued to play an important role in Imperial cult, and was frequently portrayed on coins as a symbol of the wealth and prosperity of the Roman Empire. Her primary attributes are the caduceus and cornucopia.[5] The English word "felicity" derives from felicitas.
In its religious sense, felix means "blessed, under the protection or favour of the gods; happy." That which is felix has achieved the pax divom, a state of harmony or peace with the divine world.[6] The word derives from Indo-European *dhe(i)l, meaning "happy, fruitful, productive, full of nourishment."
Also, (and this is interesting to me because Bryan recently made me aware that the Memmius to whom Lucretius addressed his poem was married to Sulla's daughter): Sulla identified himself so closely with the quality of felicitcas that he adopted the agnomen (nickname) Felix. His domination as dictator resulted from civil war and unprecedented military violence within the city of Rome itself, but he legitimated his authority by claiming that the mere fact of his victory was proof he was felix and enjoyed the divine favor of the gods.
Felicitas was a watchword used by Julius Caesar's troops at the Battle of Thapsus,[45] the names of deities and divine personifications being often recorded for this purpose in the late Republic.[46] Felicitas Iulia ("Julian Felicitas") was the name of a colony in Hispania that was refounded under Caesar and known also as Olisipo, present-day Lisbon, Portugal.[47]