Posterior comes from Latin posterior ('coming after, later, hinder'), comparative of posterus ('coming after'), from post ('after, behind'). The form is best read as a historical transfer or inheritance, with its older language material carrying the main semantic load. As an adjective and noun, it carries the sense "situated at or toward the rear; the buttocks", with the older formation still helping explain the modern use. Relevant historical forms include Latin posterior and Latin post. Derivative forms include posteriorly, posteriority; related words include posterity, post, posthumous.