"headstrong, insolent, resisting legitimate authority," c. 1600, from Latin contumaci-, stem of contumax "haughty, insolent, obstinate" (see contumely) + -ous. Related: Contumaciously; contumaciousness.
"insolent, offensive, abusive speech," late 14c., from Old French contumelie, from Latin contumelia "a reproach, insult," probably derived from contumax "haughty, stubborn, insolent, unyielding," used especially of those who refused to appear in a court of justice in answer to a lawful summons, from assimilated form of com-, here perhaps an intensive prefix (see com-), + tumere "to swell up" (from PIE root *teue- "to swell").
The unhappy man left his country forever. The howl of contumely followed him across the sea, up the Rhine, over the Alps; it gradually waxed fainter; it died away; those who had raised it began to ask each other, what, after all, was the matter about which they had been so clamorous, and wished to invite back the criminal whom they had just chased from them. [Thomas Babington Macaulay, "Lord Byron," 1877]
word-forming element making adjectives from nouns, meaning "having, full of, having to do with, doing, inclined to," from Old French -ous, -eux, from Latin -osus (compare -ose (1)). In chemistry, "having a lower valence than forms expressed in -ic."
<a href="https://www.etymonline.com/word/contumacious">Etymology of contumacious by etymonline</a>
Harper, D. (n.d.). Etymology of contumacious. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/contumacious