[pcthrowaway]

For what it's worth, I recall the CSS sprite technique being referred to as image mapping too.

Sure, it's different from the <map> element (which is officially an image map, as you say).

But it's effectively mapping out the sections of a large image that you care about and then using CSS to display parts of it

[hunter2_]

Yeah, I vaguely recall some usage like that by the same crowd that also thinks an "anchor" is specifically a fragment link that brings you to a certain element on the same page, when in reality the word applies to all <a> tags. Sort of a casual understanding of HTML among non-devs.