treasonous adj.

c. 1200, "betraying; betrayal of trust; breach of faith," from Anglo-French treson, from Old French traison "treason, treachery" (11c.; Modern French trahison), from Latin traditionem (nominative traditio) "delivery, surrender, a handing down, a giving up," noun of action from past-participle stem of tradere "deliver, hand over," from trans- "over" (see trans-) + dare "to give" (from PIE root *do- "to give"). A doublet of tradition. The Old French form was influenced by the verb trair "betray."

Vpon Thursday it was treason to cry God saue king James king of England, and vppon Friday hye treason not to cry so. [Thomas Dekker, "The Wonderfull Yeare 1603"]

In old English law, high treason (c. 1400) is violation by a subject of his allegiance to his sovereign or to the state (the sense of high here is "grave, serious"); distinguished from petit treason, treason against a subject, such as murder of a master by his servant. Constructive treason was a judicial fiction whereby actions carried out without treasonable intent, but found to have the effect of treason, were punished as though they were treason itself. The protection against this accounts for the careful wording of the definition of treason in the U.S. Constitution.

Trahison des clercs "self-compromised integrity of intellectuals, betrayal or corruption by academics, moralists, journalists, etc., of their vocation," is the title of a 1927 French work by Julien Benda, translated into English in 1928.

In short, intellectuals began to immerse themselves in the unsettlingly practical and material world of political passions: precisely those passions, Benda observed, "owing to which men rise up against other men, the chief of which are racial passions, passions and national passions." ... "Our age is indeed the age of the intellectual organization of political hatreds" he wrote. "It will be one of its chief claims to notice in the moral history of humanity." [Roger Kimball, introduction to 2007 English edition] 

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."