The Mysterious Acronym Tag
http://www.hyperwrite.com/Articles/acronym_tag.aspx

HyperWrite
2002

Abstract:

There is a seldom-used tag called 'acronym'. It was originally mark up, well, acronyms. There is a very similar tag, also seldom-used, called 'abbr', which is intended to mark up abbreviations. Both of these tags were introduced in HTML 4.0. On the face of it, apart from marking up the text, these inline tags do little else.