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

Agner Krarup Erlang
A. K. Erlang

    (1878-1929) A Danish mathematician.  Erlang the
   language and unit were named after him.

   Interested in the theory of probability, in 1908 Erlang
   joined the Copenhagen Telephone Company where he studied the
   problem of waiting times for telephone calls.

   He worked out how to calculate the fraction of callers
   who must wait due to all the lines of an exchange being in
   use.  His formula for loss and waiting time was published in
   1917.  It is now known as the "Erlang formula" and is still
   in use today.

   Biography

(http://www-history.mcs.st-andrews.ac.uk/~history/Mathematicians/Erlang.html),
   Biography
   (http://pass.maths.org.uk/issue2/erlang/index.html).

   (2005-02-26)