Earlier spellings of the town's name include Wykinglo in 1173, Wygingelow in 1185, Wykinglo in 1192, Wykinglowe in 1355.
The Swedish toponymist Magne Oftedal criticizes the usual explanation that the name comes from Old Norse Vikingr (meaning "Viking") and Old Norse ló (meaning "meadow"), that is to say "the Vikings' meadow" or "Viking's meadow". He notices that -lo was never used outside Norway (cf. Oslo) and Scandinavia. Furthermore, this word is almost never combined with a male name or a general word meaning "a category of person". Moreover, "Viking" never appears in toponymic records. For him, the first element can be explained as Uikar- or Uik- "bay" in Old Norse and the intermediate N of the old forms is a mistake by the clerks.
However, all recorded forms show this N. That is the reason why Liam Price says it is probably a Norwegian place-name and A. Sommerfelt gives it as a former Vikinga-ló and understands it as "the Vikings' meadow". Nevertheless, the Irish patronimics Ó hUiginn and Mac Uiginn (anglicized O'Higgins and Maguigan) could bring a key for the meaning "Meadow of a man called Viking".
Wykinglo was the usual name used by the Viking sailors and the traders who travelled around the Anglo-Scandinavian world. The Normans and Anglo-Normans who conquered Ireland preferred the non-Gaelic placename.
The origin of the Irish name Cill Mhantáin bears no relation to the name Wicklow. It has an interesting folklore of its own. Saint Patrick and some followers are said to have tried to land on Travailahawk beach, to the south of the harbour. Hostile locals attacked them, causing one of Patrick's party to lose his front teeth. Manntach (toothless one), as he became known, was undeterred and returned to the town, eventually founding a church. Hence Cill Mhantáin, meaning "church of the toothless one". Although its anglicised spelling Kilmantan was used for a time, it gradually fell out of use.
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