The Collaborative International Dictionary of English v.0.48:

Finn \Finn\, a.
   A native of Finland; one of the Finn? in the ethnological
   sense. See Finns.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Finns \Finns\, n. pl.; sing. Finn. (Ethnol.)
   (a) Natives of Finland; Finlanders.
   (b) A branch of the Mongolian race, inhabiting Northern and
       Eastern Europe, including the Magyars, Bulgarians,
       Permians, Lapps, and Finlanders. [Written also Fins.]
       [1913 Webster]

WordNet (r) 3.0 (2006):

Finn
    n 1: a native or inhabitant of Finland

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

finn
 v.

    [IRC] To pull rank on somebody based on the amount of time one has spent on
    IRC. The term derives from the fact that IRC was originally written in
    Finland in 1987. There may be some influence from the ?Finn? character in
    William Gibson's seminal cyberpunk novel Count Zero, who at one point says
    to another (much younger) character ?I have a pair of shoes older than you
    are, so shut up!?


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

finn

    To pull rank on somebody based on the amount of
   time one has spent on IRC.  The term derives from the fact
   that IRC was originally written in Finland in 1987.

   [Jargon File]

   (2000-08-05)