(f) Gaelic Seonag. Another feminine form of John,
less popular in Scotland than Jane or Jean. The name was often
spelt Johan in the early part of this century, and pronounced
as two syllables. This spelling is still occasionally used, together
with Johann, Johanna, Johanne. Joan swept through the English-speaking
world in the 1920’s, remaining very popular for thirty years.
In the 1970’s it has tended to be replaced by Joanne, Joanna,
To Scottish Christian Names