In zoology caudal refers to the posterior or tail end of a vertebra. With a snake it refers to the part that starts at the cloaca and goes to the tip of its tail.
Caudal is a standard anatomical term used in science and is recognized world wide. The latin form of it, caudum; means the tail. In humans the term caudum means the feet.
The term caudal (caudum) is rarely used by the general public as posterior is more easily understood by the vast majority of lay persons.