FACTBOX: Origins of Valentine's Day

(Reuters) - Valentine's Day will stoke the embers of romance worldwide on Thursday.

Here are some key facts on the day and its origins.

* POSSIBLE ORIGINS

-- Although there were several Christian martyrs named Valentine, the day probably took its name from a priest who was martyred about AD 270 by the Roman emperor Claudius II Gothicus.

According to legend, the priest signed a letter to his jailer's daughter, with whom he had fallen in love, "from your Valentine."

-- The day may also have originated in the ancient Roman celebration of the Feast of Lupercalia in honor of Juno, the queen of the Roman gods and goddesses, on February 14. Juno was also the goddess of women and marriage so honoring her was thought to be a fertility rite.

-- At the feast held the next day, the women would write love-letters and stick them in a large urn. The men would pick a letter from the urn and for the next year, pursue the woman who wrote the chosen letter. This custom lasted centuries.

* THE FIRST CARDS

-- The custom of exchanging cards and other tokens of love on February 14 began to develop in England and France in the 14th and 15th centuries and became especially popular in the United States in the 19th and 20th centuries.