1. burdensome, oppressive, or troublesome; causing hardship: onerous duties.
2. having or involving obligations or responsibilities, esp. legal ones, that outweigh the advantages: an onerous agreement.
[Origin: 1350–1400; ME <>oner?sus, equiv. to oner- (s. of onus) burden + -?sus -ous]
–adjective, -ner·i·er, -ner·i·est. Dialect
1. ugly and unpleasant in disposition or temper: No one can get along with my ornery cousin.
2. stubborn: I can’t do a thing with that ornery mule.
3. low or vile.
4.inferior or common; ordinary. [Origin: 1790–1800; contr. of ordinary]
Damn. They aren’t related.