Saint Valentine (in Latin, Valentinus) is the name of several martyred saints of ancient Rome. The name “Valentine”, derived from valens (worthy), was popular in Late Antiquity.[2] Of the Saint Valentine whose feast is on February 14, nothing is known except his name and that he was buried at the Via Flaminia north of Rome on February 14. It is even uncertain whether the feast of that day celebrates only one saint or more saints of the same name. For this reason this liturgical commemoration was not kept in the Catholic calendar of saints for universal liturgical veneration as revised in 1969.[3] But “Martyr Valentinus the Presbyter and those with him at Rome” remains in the list of saints proposed for veneration by all Catholics.[4]
In the Eastern Orthodox Church, Saint Valentine the Presbyter is celebrated on July 6,[5] and Hieromartyr Saint Valentine (Bishop of Interamna, Terni in Italy) is celebrated on July 30.
Who was Valentine?

The name “Valentine” (Priest Valentio) does not occur in the earliest list of Roman martyrs, compiled by the Chronographer of 354. The feast of St. Valentine was first established in 496 by Pope Gelasius I, who included Valentine among those “… whose names are justly reverenced among men, but whose acts are known only to God.” As Gelasius implied, nothing was known, even then, about the lives of any of these martyrs. The Saint Valentine that appears in various martyrologies in connection with February 14 is described either as:
A priest in Rome,
A bishop of Interamna (modern Terni), or
A martyr in the Roman province of Africa
St. Valentine’s Day

For more details on this topic, see Valentine’s Day.
Historian Jack Oruch has made the case that the traditions associated with “Valentine’s Day”, documented in Geoffrey Chaucer’s Parliament of Foules and set in the fictional context of an old tradition, had no such tradition before Chaucer.[17] He argues that the speculative explanation of sentimental customs, posing as historical fact, had their origins among 18th-century antiquaries, notably Alban Butler, the author of Butler’s Lives of Saints, and have been perpetuated even by respectable modern scholars. In the French 14th-century manuscript illumination from a Vies des Saints (illustration above), Saint Valentine, bishop of Terni, oversees the construction of his basilica at Terni; there is no suggestion here yet that the bishop was a patron of lovers.[18]

you teach me how to love you! but you forget to teach me how to forget you!