"Blend of Billy and Joe"
The name Billyjoe is commonly a male name from the "English" origin.
Billyjoe is a compound of the two established English given names Billy and Joe, both of which are also used as independent names in the United States. Billy is a diminutive of William and Joe is a diminutive of Joseph. The joined form first appears in US birth records in 1963, which fits a twentieth-century American combination of two existing names rather than a name inherited from an older naming tradition.
The pronunciation of Billyjoe is BIL-ee-joh.