Original: RAID is an acronym first defined by David A. Patterson, Garth A. Gibson and Randy Katz at the University of California, Berkeley in 1987 to describe a redundant array of inexpensive disks,David A. Patterson, Garth Gibson, and Randy H. Katz: A Case for Redundant Arrays of Inexpensive Disks (RAID).
Simplified: In 1988, the different types of RAID (1 to 5), were written about by David Patterson, Garth Gibson and Randy Katz in their article, called "A Case for Redundant Arrays of Inexpensive Disks (RAID)".