Late 16th century; earliest use found in John Bossewell (d. 1580), author. From post-classical Latin musion-, musio cat from classical Latin mūs + -iō.
Definition of musion in US English:
musion
nounˈmjuːsɪɒn
Heraldry historical
The wild or domestic cat, as a heraldic charge.
Origin
Late 16th century; earliest use found in John Bossewell (d. 1580), author. From post-classical Latin musion-, musio cat from classical Latin mūs + -iō.