Allen is among the fifty most common surnames in both England and Scotland.

England:

Here the name Allen derives from the old French Alain or old Breton Alan, but was originally a Germanic tribal name Alemannus, meaning “all men”.

Alan which is the name of a Welsh and Breton saint, was brought to England by Bretons in the reign of William the Conqueror.

Scotland:

Here the name has two derivations, firstly, as in the English version, it came to Scotland with the Normans. There it found popularity as a Christian name in the house of Stewart and quickly spread.

The second derivation is Ailin and comes from the Gaelic Ail, meaning rock. This gave rise to the names M^cAilin and M^cAllen

Ireland:

The Allens here mainly settled in Counties Armagh and Antrim. While the majority of Allens are undoubtedly of English or Scottish extraction, there are families who can claim to be indigenous Irish as names like O’Haillin became anglicised.