The name Glen is a Scottish English name derived from the Gaelic word "gleann," which means "valley." It is believed to have originated as a topographic name, referring to someone who lived near or in a valley. The name has been in use since the Middle Ages and has a long and rich history.

One of the earliest recorded instances of the name Glen is in the Scottish Exchequer Rolls of 1264, where it appears as "Glendonyn." This suggests that the name was already in use in Scotland by the 13th century. The name also appears in various historical records and documents throughout the centuries, such as the Ragman Rolls of 1296 and the Bain's Calendar of Documents relating to Scotland from 1357.

In terms of famous bearers of the name, one of the earliest known figures was Glen Cuyn (born around 1120), a Scottish nobleman and landowner who held lands in Ayrshire. Another notable figure was Glen Urquhart (born around 1260), a Scottish chieftain and warrior who fought in the Wars of Scottish Independence.

During the Renaissance period, the name gained popularity across Europe. One of the most famous bearers of the name was Glen Leyburn (1525-1584), an English Protestant reformer and bishop of Carlisle. Another notable figure from this era was Glen Riddell (1564-1628), a Scottish mathematician and astronomer who made significant contributions to the field of navigation.

In more recent history, the name has continued to be popular, particularly in English-speaking countries. One of the most famous bearers of the name was Glen Miller (1904-1944), the American big band leader and trombonist who became one of the most popular musicians of the swing era.

Other notable figures with the name include Glen Cunningham (1909-1988), an American athlete and Olympic gold medalist in the 1500 meters; Glen Sather (born 1943), a Canadian former ice hockey player and coach; Glen Hansard (born 1970), an Irish musician and actor; and Glen Keane (born 1954), an American animator and illustrator who worked for Disney.