Hallux: What the ancient Romans called the big toe. Since hallux was a good enough word for the big toe among the ancient Romans, it has long done yeoman's duty in medicine. Abnormalities of the big toe tend thus to be called hallux this-or-that.
For example, hallux valgus and hallux varus. In hallux valgus, the big toe is bent outward (valgus) so it overlaps the 2nd toe. In hallux varus, the big toe is bent inward (varus) at the joint.