It seems I've been mispronouncing this -- I put the stress on the fourth syllable. Ah, well. First borrowed in 1652 in the sense of the learned preamble to a book from Greek, where it is the neuter passive present participle of prolegein, to say beforehand, from pro-, before + legein, to speak (the root of lecture). Preface is the exact same meaning, only from Latin roots.
Some people see death as a prolegomenon to another life.