Primordial, an adjective, describes something that has been around forever, like cockroaches.
Primordial comes from the Latin words primus, meaning "first" and ordiri, "to begin." So it is easy to see that this adjective means "first of all, original." When something is primordial, it has existed since the earliest time, like the primordial mud some scientists believe was the source of all life on Earth. Remember that is it a scientific term — don't call your teacher primordial just because she's been teaching at your school since it opened.