The name is attested with some frequency in Medieval Germany during the 8th to 11th centuries, as Arnold, Arnalt, Arnald, Arnolt.

It was occasionally spelled Harnold, Harnald, and the name may have been conflated with an independent formation containing hari- "host, army".

However, the Norman spelling did not survive into the modern period (other than a possible survival in surnames such as Arnall, Arnell, although these names could be of multiple origins, most likely the Old English), and once standardised spelling swept England, the form Arnold gradually became the norm.

In the United States, Arnold had a relative surge of popularity at the beginning of the 20th century, peaking as the 89th most commonly given masculine name in 1916, but it dropped again below rank 200 by the 1950s.

The German name was also adopted in Old West Norse (14th century), as Arnaldr (Icelandic: Arnaldur).