E. Cobham Brewer 1810–1897. Dictionary of Phrase and Fable. 1898.
Ex’on,
Exon of the Guards. Any one of the three certain officers of the day in command of the yeomen of the royal guard; the acting officer who resides at the court; an exempt. Capitaines exempts des gardes du corps. (French, exoine, ex soin, exempt from duty or care.)
