[name]Johanne[/name], being a feminization of [name]John[/name] (the English form of the Hebrew name Yochanan via Greek [name]Ioannes[/name] to Latin Iohannes), seems to point to [name]Jane[/name]. See the entry for [name]Jane[/name] as well as International variations of [name]Jane[/name]. Perhaps your relatives “invented” [name]Johanne[/name], but more likely they heard it around. [name]Johanna[/name] is a real name in other parts of the world, and my parents were friends with a [name]Johanna[/name] in NY in the 1950s so not unheard in the US. It is the feminine form of f [name]Johan[/name] and [name]Johann[/name], which are forms of [name]John[/name] in places like Germany and some Scandinavian countries. Usually there, the J is pronounced like a Y, simulating the I in earlier forms, by my parents’ friend pronounced it with a J-J-J, [name]JoHANna[/name], not [name]Yo[/name]-Hah-na.
Try these lists and see if you find something you like:
[name]Joanne[/name]/[name]Joanna[/name] may also seem like a blend of [name]Jo[/name] ([name]Josephine[/name]) and [name]Anna[/name] (and in some cases of the name, may be intended as such), but it is derived from [name]Johanna[/name]:
****Rather than copy/paste the urls to pages, it is easier to look up [name]Johanna[/name] and [name]Jane[/name] and click around. Beneath some names, there is a list of LISTS with more names, such as international variations, and within each entry, some names link to other entries.