Shannen is of Irish origin, derived from the surname Ó Seanáin, which means 'descendant of John'. It is pronounced as /ˈʃænən/. The name gained popularity in the 1980s and 1990s, partly due to its use by American actress Shannen Doherty.
The name Shannen experienced fluctuations in popularity over the years, with peaks in the late 90s and early 2000s, but it has generally been a less common choice compared to many other names.