A name preserved more by footnotes than fame. Didymus of Alexandria (dates uncertain) is a shadowy figure known not for his life, but for a handful of mathematical fragments included in Heiberg’s Mathematici Graeci Minores. We don’t know who he was, when exactly he lived, or whether he’s the same as the famous grammarian — and honestly, probably not. What we do have are glimpses of mathematical commentary that echo the rigor of a thinker who slipped through history’s cracks.