The Collaborative International Dictionary of English v.0.48:

Spool \Spool\ (sp[=oo]l), n. [OE. spole, OD. spoele, D. spoel;
   akin to G. spule, OHG. spuola, Dan. & Sw. spole.]
   A piece of cane or reed with a knot at each end, or a hollow
   cylinder of wood with a ridge at each end, used to wind
   thread or yarn upon.
   [1913 Webster]

   Spool stand, an article holding spools of thread, turning
      on pins, -- used by women at their work.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Spool \Spool\, v. t. [imp. & p. p. Spooled (sp[=oo]ld); p. pr.
   & vb. n. Spooling.]
   To wind on a spool or spools.
   [1913 Webster]

WordNet (r) 3.0 (2006):

spool
    n 1: a winder around which thread or tape or film or other
         flexible materials can be wound [syn: bobbin, spool,
         reel]
    v 1: transfer data intended for a peripheral device (usually a
         printer) into temporary storage
    2: wind onto a spool or a reel

V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

SPOOL
       Simultaneous Peripheral Operations OnLine


The Jargon File (version 4.4.7, 29 Dec 2003):

spool
 vi.

    [from early IBM ?Simultaneous Peripheral Operation On-Line?, but is widely
    thought to be a backronym] To send files to some device or program (a
    spooler) that queues them up and does something useful with them later.
    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. See also demon.


The Free On-line Dictionary of Computing (30 December 2018):

SPOOL

    Acronym for Simultaneous Peripheral
   Operation On-Line; but see also spool.

   [Jargon File]

   (1996-05-20)


The Free On-line Dictionary of Computing (30 December 2018):

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)].

   [Jargon File]

   (1995-03-25)


The Free On-line Dictionary of Computing (30 December 2018):

spool

    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"?]

   [Jargon File]

   (1996-05-20)