This name has been common (in various spellings) throughout the Christian world, and it became very popular in the Middle Ages. Saint Andrew is regarded as the patron of Scotland, Russia, Greece and Romania. The name has been borne by three kings of Hungary, American president Andrew Jackson (1767-1845), and, more recently, English composer Andrew Lloyd Webber (1948-).
Famous bearers include the Welsh poet Dylan Thomas (1914-1953) and the American musician Bob Dylan (1941-), real name Robert Zimmerman, who took his stage surname from the poet's given name. Due to those two bearers, use of the name has spread outside of Wales in the last half of the 20th century. It received a further boost in popularity in the 1990s due to a character on the television series Beverly Hills 90210.
As a given name, it took off in popularity during the 1990s. It has been more common for girls in the United States probably because of its similarity to other names such as Megan, Morgan and Regan.
In England the name was used by the Normans and became very popular due to Saint Thomas Becket, a 12th-century archbishop of Canterbury and martyr. It was reliably among the top five most common English names for boys from the 13th to the 19th century, and it has remained consistently popular to this day.
Another notable saint by this name was the 13th-century Italian philosopher and theologian Thomas Aquinas, who is regarded as a Doctor of the Church. Other famous bearers include philosopher Thomas Hobbes (1588-1679), American president Thomas Jefferson (1743-1826), novelist Thomas Hardy (1840-1928), and inventor Thomas Edison (1847-1931).
This name was later borne by three other English kings, as well as rulers of Scotland, Sicily (of Norman origin), the Netherlands and Prussia. Other famous bearers include William Wallace, a 13th-century Scottish hero, and William Tell, a legendary 14th-century Swiss hero (called Wilhelm in German, Guillaume in French and Guglielmo in Italian). In the literary world it was borne by dramatist William Shakespeare (1564-1616), poet William Blake (1757-1827), poet William Wordsworth (1770-1850), dramatist William Butler Yeats (1865-1939), author William Faulkner (1897-1962), and author William S. Burroughs (1914-1997).
In the American rankings (since 1880) this name has never been out of the top 20, making it one of the most consistently popular names (although it has never reached the top rank). In modern times its short form, Liam, has periodically been more popular than William itself, in the United Kingdom in the 1990s and the United States in the 2010s.