The Free On-line Dictionary of Computing (19 January 2023):

YAUN

   /yawn/ Yet Another Unix Nerd.

   Reported from the San Diego Computer Society (predominantly a
   microcomputer users' group) as a good-natured punning insult
   aimed at Unix zealots.

   [Jargon File]

   (1994-11-11)


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

YAUN
 /yawn/, n.

    [Acronym for ‘Yet Another Unix Nerd’] Reported from the San Diego Computer
    Society (predominantly a microcomputer users' group) as a good-natured
    punning insult aimed at Unix zealots.