Vicious
Middle English (in the sense ‘characterized by immorality’): from Old French vicious or Latin vitiosus, from vitium ‘vice’.
wiktionary
From Middle English vicious, from Anglo-Norman vicious, (modern French vicieux), from Latin vitiōsus, from vitium(“fault, vice”). Equivalent to vice + -ous.
etymonline
vicious (adj.)
late 14c., "unwholesome, impure, of the nature of vice, wicked, corrupting, pernicious, harmful;" of a text, "erroneous, corrupt," from Anglo-French vicious, Old French vicios "wicked, cunning, underhand; defective, illegal" (Modern French vicieux), from Latin vitiosus (Medieval Latin vicious) "faulty, full of faults, defective, corrupt; wicked, depraved," from vitium "fault" (see vice (n.1)).
Meaning "inclined to be savage or dangerous" is first recorded 1711 (originally of animals, especially horses); that of "full of spite, bitter, severe" is from 1825. In law, "marred by some inherent fault" (late 14c.), hence also this sense in logic (c. 1600), as in vicious circle in reasoning (c. 1792, Latin circulus vitiosus), which was given a general sense of "a situation in which action and reaction intensify one another" by 1839. Related: Viciously (mid-14c., "sinfully"); viciousness.
