From an Old French name of Germanic (Frankish) origin, from berht ‘bright, famous’ + hramn ‘raven’. Ravens were traditional symbols of wisdom in Germanic mythology; Odin was regularly accompanied by ravens called Hugin and Munin. This name was adopted by the Normans and introduced by them to Britain. See also Bertrand.
German: from Adler ‘eagle’, denoting someone living in a house identified by the sign of an eagle. The German noun is from Middle High German adelar, itself a compound of adel ‘noble’ + ar ‘eagle’. This name is widespread throughout central and eastern Europe, being found for example in Czech, Polish, Slovenian, and Hungarian (Ádler).