Allen peaked in 1951 and currently holds rank #573, with 271,282 total SSA bearers — one of the larger totals in this rank range. The name spent most of the mid-20th century as a reliable choice, close to but slightly less common than Alan and Allan, and has been declining since roughly 1960. It's a name in the waiting room of revival.
Celtic Roots, Many Spellings
Allen, Alan, and Allan all trace to a Celtic root of uncertain meaning — possibly from the Breton name Alain, possibly related to words for "rock" or "harmony." The Normans brought Alan to England; it spread across England, Scotland, and Wales; and the various spellings emerged as different communities standardized their own orthography. Allen became the preferred American spelling in the 20th century, particularly in the South and Midwest, while Alan stayed more common in Britain. None of the spellings has a decisive claim to priority.
The Allen Roster
The name has extraordinary coverage in American culture: Woody Allen defined an era of neurotic cinema; Allen Ginsberg transformed American poetry; Tim Allen built a TV career across decades; Lily Allen (a woman) complicates the gendering. In sports, Allen Iverson is among the most stylistically influential basketball players in history. The name has range from comedy to literature to athletics, which is either a sign of its breadth or a sign that it's been used so widely that famous bearers span every category by coincidence.
The Waiting Room
Allen is where 1950s names currently live: not vintage enough to feel charming again, not recent enough to feel contemporary. Frank, Walter, and Harold crossed back into favor in the 2010s; Allen may follow in the late 2020s or 2030s. For parents willing to arrive early, Allen is genuine, understated, and free of crowding. The current class of baby Allens will be nearly alone with the name for years. Compare it with Alan or Alden for the fuller picture of this name family.