- Star Tales - Triangulum (ianridpath.com)
Since any three points make up the corners of a triangle it is unsurprising, if somewhat unimaginative, to find a triangle among the constellations. Aratus and Eratosthenes knew this constellation as Δελτωτόν (Deltoton), because its shape resembled a capital delta (Δ), while Ptolemy in the Almagest listed it as Τρίγωνον (Trigonon), triangle.