An infORmal generic term fORfloating-headmagnetic 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). [Jargon File] (1994-12-06)