In the original definition, from 1991, we believed that the original bug was a 2-inch moth in a valve. I now believe that a) it wasn’t 2 inches b) it wasn’t really a software bug.
But debugging was involved and it was a computer bug. The idea of removing bugs from a machine is now attributed to Thomas Edison.
As opposed to the original bug (a 2-inch moth in a valve).
From the original SB.txt