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

thin client
light client

    A simple client program or hardware device
   which relies on most of the function of the system being in
   the server.

   Gopher clients, for example, are very thin; they are
   stateless and are not required to know how to interpret and
   display objects much more complex than menus and plain text.
   Gopher servers, on the other hand, can search databases and
   provide gateways to other services.

   By the mid-1990s, the model of decentralised computing where
   each user has his own full-featured and independent
   microcomputer, seemed to have displaced a centralised model
   in which multiple users use thin clients (e.g. dumb
   terminals) to work on a shared minicomputer or mainframe
   server.  Networked personal computers typically operate as
   "fat clients", often providing everything except some file
   storage and printing locally.

   By 1996, reintroduction of thin clients is being proposed,
   especially for LAN-type environments (see the cycle of
   reincarnation).  The main expected benefit of this is ease of
   maintenance: with fat clients, especially those suffering from
   the poor networking support of Microsoft operating
   systems, installing a new application for everyone is likely
   to mean having to physically go to every user's workstation to
   install the application, or having to modify client-side
   configuration options; whereas with thin clients the
   maintenance tasks are centralised on the server and so need
   only be done once.

   Also, by virtue of their simplicity, thin clients generally
   have fewer hardware demands, and are less open to being
   screwed up by ambitious lusers.

   Never one to miss a bandwagon, Microsoft bought up Insignia
   Solutions, Inc.'s "NTRIGUE" Windows remote-access product
   and combined it with Windows NT version 4 to allow thin
   clients (either hardware or software) to communicate with
   applications running under on a server machine under Windows
   Terminal Server in the same way as X had done for Unix
   decades before.

   (1999-02-01)