I knew we had to have some colors so Ruff Pleasant, who was later governor of Louisiana, a couple of other men and I went to Reymond’s store, at that time at the corner of Third and Main streets. We told them we wanted quite a lot of ribbon for colors, but no one knew what our colors were. It happened that the store was stocking ribbon for the coming Carnival season and had a large supply of purple and gold. The green had not yet come in. So we adopted the purple and old gold, bought out the stock, and made it into rosettes and badges. Purple and old gold made a good combination and we have stuck to it ever since.

...
It was the custom at that time, for some occult reason, to call football teams by the names of vicious animals; the Yale Bulldogs and the Princeton Tigers, for example. This is still the vogue. It struck me that purple and gold looked Tigerish enough and I suggested that we choose “Louisiana Tigers,” all in conference with the boys. The Louisiana Tigers had represented the state in Civil War and had been known for their hard fighting. This name was applied collectively to the New Orleans Zouaves, the Donaldsonville Cannoniers, and to a number of other Louisiana companies sent to Virginia, who seemed to have the faculty of getting into the hardest part of the fighting and staying there, most of them permanently. One company I knew of went in 200 strong; only 28 returned and many of these were wounded.

So "Louisiana Tigers" went into the New Orleans papers and became our permanent possession.

...
A few years later when Col. David F. Boyd, who had been president of the University from 1865 to 1880 and again from 1884 to 1886, returned to the University, he was rather surprised to find purple and gold as the colors. He told me they were not the colors, that white and blue had been chosen by him many years ago. But purple and gold had by that time established itself and nothing was ever done about it. Colonel "Dave" also liked the name, "Tigers." I think he was one of them himself during the Civil War.

whole story as op: LINK