Triangulum lies just south of Andromeda on the edge of the Milky Way.
The best description was by the Greek poet-astronomer Aratos translated by a Mr. Brown. He says:
“Below Andromeda, in three measured
like to Delta; equal two of them.”
Transcribed by Cicero as Deltoton, naturally it was the Delta of the Nile of Egypt.
Thus it was more important to the Egyptians than to the modern astronomers.
The Protestant lawyer Johann Bayer in the sixteenth century thought it astrologically represented the three known continents of the Earth: Europe, Asia and Africa. Bayer was in conflict with the Roman church, which thought it represented the Trinity or the Miter of Saint Peter.