Why were the "McWillie Blues" (Co. K, 3rd MS Infantry) so named?

There are only four Mississippians in CS service named "McWillie," and none of them seem to be associated with this company or the 3rd MS.

Was McWillie a benefactor of the company, perhaps equipping them for the war?

The question isn't of great importance; I'm just incredibly curious, as the company keeps cropping up in my reseach on the Seven Stars Artillery, since both companies were raised in Copiah Co., MS.

Thanks! -- Jim "Enquiring/Inquiring Mind" Huffman, Seven Stars Artillery