This name spiked in popularity in several places around the world in 1954 after Pope Pius declared it to be a Marian year, in honour of the Virgin Mary. A similar declaration in 1987 did not have as marked an effect.
The name was introduced to the English-speaking world by E. D. E. N. Southworth's novel Gloria (1891) and George Bernard Shaw's play You Never Can Tell (1898), which both feature characters with a Portuguese background [1]. It was popularized in the early 20th century by American actress Gloria Swanson (1899-1983). Another famous bearer is feminist Gloria Steinem (1934-).