The Collaborative International Dictionary of English v.0.48:

Ya \Ya\ (y[aum]), adv.
   Yea. [Obs.] --Chaucer.
   [1913 Webster]

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

YA-
 abbrev.

    [Yet Another] In hackish acronyms this almost invariably expands to Yet
    Another, following the precedent set by Unix yacc(1) (Yet Another
    Compiler-Compiler). See YABA.


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

Yet Another
YA-

    (YA-, after Unix's yacc - Yet Another
   Compiler-Compiler) A humorous allusion often used in titles to
   acknowledge that the topic is not original, though the content
   is.  As in "Yet Another AI Group" or "Yet Another Simulated
   Annealing Algorithm".  If used of others' work, it
   describes something of which there are already far too many.

   In hackish acronyms the "YA" prefix almost invariably expands
   to Yet Another, e.g. YABA, YAUN.

   [Jargon File]

   (1996-11-26)