I musta glossed over that. Anyway....to me, having been involved in the arcade industry for over 20 years...."kick harness" means the wiring harness to a dedicated Kick game. I've never heard that term applied to anything else. A more accurate term would be auxiliary harness. Like the add-ons they did with the jamma setup for the SF games that didn't have enough available wires on a regular Jamma harness to deal with the extra buttons it used.
Perhaps you glossed over the 1990's too.

You may not be a "fighting games kid", but having been involved in the industry for 20+ years like you say, undoubtedly you've must have come across a few nicknames for an auxiliary harness. Kick harness, Jamma plus harness, Extra button harness, these are the terms most people use today. Prior to the 90's, sure, Kick Harness meant the harness for the game - Kick.
@rapomstage3
You can easily find them on ebay for cheap. Just do a search for "Kick harness" and you'll find about 10 or so listings. jammaboards.com, as well as bob roberts also have them. They're easy to make yourself, but if you're not confident with cutting/crimping wires then paying $15 or so for a pro-built one isn't a bad idea.