calumnious (adj.)

mid-15c., "false accusation, slander," from Old French calomnie (15c.), from Latin calumnia "trickery, subterfuge, misrepresentation, malicious charge," from calvi "to trick, deceive."

According to de Vaan, PIE cognates include Greek kēlein "to bewitch, cast a spell," Gothic holon "to slander," Old Norse hol "praise, flattery," Old English hol "slander," holian "to betray," Old High German huolen "to deceive." The whole group is perhaps from the same root as call (v.). A doublet of challenge.