From The Collaborative International Dictionary of English v.0.48 [gcide]:
Ganza \Gan"za\, n. [Sp. gansa, ganso, goose; of Gothic origin.
See Gannet, Goose.]
A kind of wild goose, by a flock of which a virtuoso was
fabled to be carried to the lunar world. [Also gansa.]
--Johnson.
[1913 Webster]