Acronym for Simultaneous Peripheral Operation On-Line; but see also spool.
An object-oriented logic programming language.
["An Experience with a Prolog Based Language", K. Fukunaga et al, SIGPLAN Notices 21(11):224-231 (Nov 1986) (OOPSLA '86)].
To send files to some device or program (a "spooler" or demon) that puts them in a queue for later processing of some kind. Without qualification, the spooler is the "print spooler" controlling output of jobs to a printer; but the term has been used in connection with other peripherals (especially plotters and graphics devices) and occasionally even for input devices.
The term "SPOOL" has been attributed to IBM as an acronym for Simultaneous Peripheral Operation On-Line but it's widely thought to have been contrived for effect.
[No connection with "spool of magnetic tape"?]