This Latin phrase means "nothing comes from nothing." It appears in De Rerum Natura (On the Nature of Things) by the Roman poet-philosopher Titus Lucretius Carus (98-55 B.C.), who - picking up on the thought of the Greek philosopher Parmenides (c.540-480 B.C.) - makes it his first principle for understanding the nature of all things.
Grendel thinks, "Nihil ex nihilo" at the end of chapter 10 (150). He is fitful, ill at ease, troubled in his sleep in the wake of the Shaper's funeral. Could he actually be missing the old man?
This tenth chapter ends with a number of vague forbodings. And Grendel has met another monster, "an old woman wild as the wind." Who is this?
Also, could Grendel himself be the nothing from which nothing comes?
This concept is only tangentially related to the philosophy of nihilism.