Inveteracy

Webster's Dictionary of the English Language

·noun Malignity; spitefulness; virulency.

II. Inveteracy ·noun Firm establishment by long continuance; firmness or deep-rooted obstinacy of any quality or state acquired by time; as, the inveteracy of custom, habit, or disease;

— usually in a bad sense; as, the inveteracy of prejudice or of error.