Winchester

n. Informal generic term for 'floating-head' magnetic-disk drives in which the read-write head planes over the disk surface on an air cushion. The name arose because the original 1973 engineering prototype for what later became the IBM 3340 featured two 30-megabyte volumes; 30--30 became 'Winchester' when somebody noticed the similarity to the common term for a famous Winchester rifle (in the latter, the first 30 referred to caliber and the second to the grain weight of the charge).