English from the Latin feminine form of John [q.v.] ultimately from the Greek Ioannes, from Hebrew name Yochana meaning "God has been gracious"; NT Luke 8:3, 24:10.
In the 1841 Census of Aberdeenshire a number of spelling variations occur, many re-inserting the "h": Johanna. Note that these variants may not be found with basic Soundex searches.
Joanna and Johanna are Latin forms of Joan, used in old documents with appropriate Latin endings.