Welsh and English, from Old English "friend of peace". It was derived from the Welsh name Gwenfrewi "holy reconciliation" and altered to adopt the Old English meaning.
Winifred is also used as an Anglicised form of the Irish Oonagh/Oona. The English spelling is Una
There are a number of spelling variations which should all be returned by Soundex searches of official databases. In old documents the form Guinevra may be found, with appropriate Latin case endings.