The original origin of Arlo is unclear. It is thought to be derived from the Anglo-Saxon name Harlow, from the elements hoer and hlaw, meaning "rock hill." In some regions of England, Arlo translates to "fortified hill." The name was first mentioned in The Faerie Queene, Edmund Spenser’s 1590 poem. In this context, the name is thought to be derived from the Irish-Gaelic Aherlow meaning "between two highlands." It could also be from Spanish, meaning bayberry tree. The name’s popularity has only increased into the 21st century and is currently on an upward trend.