until 19th C was probably most common Manx female forename (tho it does not appear in talbots 1511/1515 manorial rolls!) - possibly from Johanna (latin feminine form of John) but probably (acc to W H Gill) from Jonet - the Old Sc. form of Janet. Sc. Gaelic Sionaid.

"Popularly but erroneously equated with Judith perhaps because of the resemblance of Juney to Judy, which was also popular."