The suggestion that the spelling Perlo probably represents a Continental Germanic name (Forssner 1916: 204; von Feilitzen 1937: 344) is not especially persuasive, in part because there is no obvious CG name which it might represent, and in part because its only bearer in DB was a small landowner in Somerset who is unlikely to have had a name of Continental origin and in any case was very probably called Perle, not Perlo (Perle 2).
A more satisfactory working hypothesis is that Perle originated as an Old English nickname. The surname Perle occurs from the thirteenth century onwards in other parts of the country, perhaps providing independent evidence for the OE forename. Reaney’s suggestion (1997: 343) that the surname was coined from the noun perle (‘pearl’) in reference to a seller of pearls is not at all convincing.
Latin perla for a pearl appears to have been borrowed into Old English by the later tenth century, when Ælfric of Eynsham glossed Latin enula and gemmula (‘small gem’) as pærl (Zupitza 1880: 304), though the recorded history of the word remains tantalizingly uncertain (OED: pearl, n.1 and adj.).
Forssner 1916: Thorvald Forssner, Continental-Germanic Personal Names in England in Old and Middle English Times (Uppsala: K. W. Appelbergs, 1916)
Reaney 1997: P. H. Reaney, A Dictionary of English Surnames, 3rd edn with corrections and additions by R. M. Wilson (Oxford: Oxford University Press, 1997)
von Feilitzen 1937: Olof von Feilitzen, The Pre-Conquest Personal Names of Domesday Book, Nomina Germanica 3 (Uppsala: Almqvist and Wiksells, 1937)
Zupitza 1880: Ælfrics Grammatik und Glossar, ed. J. Zupitza (Berlin, 1880)
Spellings in Domesday Book: Perlo
Forms in modern scholarship:
von Feilitzen head forms: Perlo
Phillimore edition: Perlo
Alecto edition: Perlo