This term came from printing and publishing, where described the notes on layout or the corrections to make during editing, but the practice of adding annotations to documents goes back to the beginning of writing.
It now means instructions or descriptions added to a computer document to act as guidelines for identification or formatting. Markup has been around for a very long time.
|Anon, ‘Leabhar na h-Uidhri: The Book of the Dun Cow’||1100|
|Marjorie Kinnan Rawlings, ‘Scribner’s Magazine’||1932|
|.h1 Interest Rates||Runoff, Script||1960s|
|<sec><ttl>Interest Rates</ttl>...||SGML (AAP)||1985|
|<div1><head>Interest Rates</head>...||SGML (TEI)||1989|
|<H1>Interest Rates</H1>||SGML (HTML)||1989|
|<sect1><title>Interest Rates</title>||XML (DocBook)||1995|
|<h1>Interest Rates</h1>||XML (HTML5)||2005|
Some of the history of computer markup can be seen in the names (h1 and H1, section, sec, sect1, etc). Anglo-American influence in computing means most common systems are based on English-language names, although they can be used in any language.