Legend has it that the name came from the red color of water that got into the river when the Red River flooded. It sounds plausible. Levees now keep the Red from flowing into the Vermilion, but in earlier times the two were connected through a series of waterways.
But that's not the only theory about how the river got its name.
According to a 1976 article by Albert Gaude, who was then curator of natural science at the Lafayette Natural History Museum and Planetarium, there are three major theories about the name.
According to the first one, settlers who came up Bayou Vermilion saw Red River soil deposits on either side of the bayou as far downstream as the community of Long Bridge (where the Breaux Bridge highway crosses the Vermilion Bayou).
This soil ranges from a brown to a bright red color, especially when it is wet. As the color vermilion is defined as "a vivid red to reddish orange," Gaude says "it would seem apt for the early discoverers to name this stream for its brightly colored banks."
He notes that the early spelling of the river's name was Vermillion, as it would be spelled in French, but that the English spelling, Vermilion, was later adopted.
In some Spanish documents the stream is called Rio Bermellon, and it is described as running from the "pubelo of St. Landri' through "atacapas country" down to the Bahia de Bermellon (Vermilion Bay).
A second theory for the river's name concerns the tiny Azolla caroliniana fern, sometimes called mosquito fern, which grows on the surface of sluggish streams in the South.
Under a canopy of trees, it can form dense sheets of vegetation that cover the surface of the stream, but, Gaude notes, "when the sun's rays reach the surface of the water with full intensity, these dense green mats turn to a uniform 'autumnal red' color." These sheets can be regularly seen along several stretches of the river.
The last theory involves the Attakapas, probably the earliest settlers of the area, who sometimes used a reddish ochre as body paint.
But when Europeans came to the area, they brought a new powder called "Vermilion" which was made from cinnabar and was a much-brighter red. They traded this powder with the Attakapas in exchange for furs and other goods.
Gaude suggests that the river could have gotten its name because of the unusually heavy trading in the red powder.
We know that there were several Attakapas villages on the river that might have provided fertile trading ground.
You can contact Jim Bradshaw at firstname.lastname@example.org or P.O. Box 1121, Washington LA 70589.