The use of the word ''server'' in computing comes from [[queueing theory]],<ref>{{cite book |title=Desktop computers: in perspective |author=Richard A. Henle |author2=Boris W. Kuvshinoff |author3=C. M. Kuvshinoff |publisher=Oxford University Press |year=1992 |url=https://books.google.com/books?id=g4krAAAAYAAJ&q=server+%22queuing+theory%22 |page=417 |isbn=978-0-19-507031-6 |quote=Server is a fairly recent computer networking term derived from queuing theory.}}</ref> where it dates to the mid 20th century, being notably used in {{Harvtxt|Kendall|1953}} (along with "service"), the paper that introduced [[Kendall's notation]]. In earlier papers, such as the {{Harvtxt|Erlang|1909}}, more concrete terms such as "[telephone] operators" are used.
In computing, "server" dates at least to RFC 5 (1969),<ref name="rulifson">{{cite IETF |title=DEL |rfc=5 |last=Rulifson |first=Jeff |author-link=Jeff Rulifson |date=June 1969 |publisher=[[Internet Engineering Task Force|IETF]] |access-date=30 November 2013}}</ref> one of the earliest documents describing [[ARPANET]] (the predecessor of [[Internet]]), and is contrasted with "user", distinguishing two types of [[Host (network)|host]]: "server-host" and "user-host". The use of "serving" also dates to early documents, such as RFC 4,<ref>{{cite IETF |title=Network Timetable |rfc=4 |last=Shapiro |first=Elmer B. |date=March 1969 |publisher=[[Internet Engineering Task Force|IETF]] |access-date=30 November 2013}}</ref> contrasting "serving-host" with "using-host".
The [[Jargon File]] defines ''server'' in the common sense of a process performing service for requests, usually remote,<ref>[http://www.catb.org/jargon/html/S/server.html server]</ref> with the 1981 version reading:<ref>[http://www.catb.org/jargon/oldversions/jarg110.txt]</ref>
{{quote |SERVER n. A kind of [[Daemon (computing)|DAEMON]] which performs a service for the requester, which often runs on a computer other than the one on which the server runs.}} The average utilization of a server in the early 2000s was 5 to 15%, but with the adoption of virtualization this figure started to increase to reduce the number of servers needed.<ref>{{cite web | url=https://semiengineering.com/chip-aging-accelerates/ | title=Chip Aging Accelerates | date=14 February 2018 }}</ref>
The average utilisation of a server in the early 2000s was 5 to 15%, but with the adoption of this figure started to increase to reduce the number of servers needed.
