I think Dr. John above is right with his "conveniently rhyming surname" remark.

It has always seemed to me, though with no evidence either way, that the name is too convenient and too unlikely. Along the lines of

"This song it was written
By Smedley K. Smitten" or

"This song was composed
By Tuby T. Rose,
Several weeks after the news did arrive
To give time for reflection
Before the big election,
And then from hist'ry take his dive." etc.

Sorry for the irreverence, but I just never could take Mr. Gashade seriously. On the other hand Dylan brilliantly made a character out of Judas Priest. Perhaps the Great American Novel about Billy Gashade is yet to be written.

Bob