I have no idea about this particular case, but for a lot of older concepts the root of divergent terminology is IBM. IBM invented its own lingo for lots of things, and persisted in using it even when the rest of the world settled on a different term. (This seems to be a habit companies pick up when they become huge and dominant; see also Micro-speak and Google-speak.)

The thing everybody else called a "hard disk," for instance, was long referred to by IBMers as either a "Winchester disk" (see https://en.wikipedia.org/wiki/History_of_IBM_magnetic_disk_d... for the etymology on that one) or a "fixed disk."