ETYMOLOGY
from Latin onerarius (suitable for carrying a burden or cargo) + -ous
EXAMPLE
“… For that he emongest all gouernors, chiefly did remembre that a kyng ought to bee a ruler with wit, grauitie, circumspeccion, diligence and constancie, and for that cause to haue a rule to hym comitted, not for an honor, but for an onorarious charge and daily burden, and not to looke so muche on other mennes liuynges, as to consider and remembre his owne doynges and propre actes. …”
From: The vnion of the two noble and illustrate famelies of Lancastre [and] Yorke
By: Edward Hall, 1548
Lexicophilia 