It's a longstanding abbreviation for "accessibility", along the same lines of i18n being an abbreviation for internationalisation. There's the first letter, and the last letter, and between them a count of the number of letters elidded.
Greek, Latin and <tech lingo>.
The Greek/Latin/<jargon> structure should be standard or taught in schools in some capacity.
Basic programming concepts are popular, useful and should probably be taught as a sub category of English... given that programming is supposed to be a language, and pull its roots (somewhat) from English or "natural language".
Society would produce higher quality code if the basic concepts were considered as a literacy requirement for children.
It's certainly not widespread. Or at least, this is the first time I've ever seen it.