Saint Valentine is the anglicized name for Valentinus. There were at least two saints named this. St. Valentine of Rome who was a priest and martyred on February 14, 269 AD. Also, St. Valentine of Terni was a bishop of Interamna who was martyred on February 14, 197 AD. Why don't we know about them? Because the Roman empire didn't keep much documentation on Christian activities, because they were thought unimportant and few Christians back then were literate.
Valentinus comes from the Latin word "valere" meaning to be strong or powerful. It is the root of the word valient.
The holy day did not become associated with "romantic love" until nearly 1500 years later in the late 18th century!
Please do not copy or re-post photographs of my daughter.