Bull

Bull meaning to deceive dates from the 1500s and is thought to derive from the Old French boler or bouler meaning to deceive. It has nothing whatsoever to do with the animal. By the 1600s, it had come to mean deceive with empty or misleading talk. The OED still maintains that the origin is unknown but for most other etymological sources, the foregoing origin suffices. See also Bullshit and Cock and bull story.