This is an eye-catching word, a word you probably didn’t know to exist. It has a certain zest – one might even think it sexy. Some people might think it has no vowels, but of course you can hear the vowel when you say it: /zɪst/. The y is used to spell the vowel sound. And the x is used to spell /z/ for no other reason than that English does not currently permit a /ks/ onset (or a /gz/ one).
Does its form give any clue as to its meaning? Perhaps it got mixed up trying to cross the Styx? Or is it a particularly male (xy) street (st) (or does that seem sexyst)? The latter might seem closer to what it is. The source is ultimately Greek ξυστός xustos “polished”, which in this case refers to a polished marble floor in a porch or portico of a gymnasium, and thus to the porch or portico itself, where exercises (such as wrestling) would take place during poor weather. By extension it also came to refer to the whole gymnasium building.
The Romans took up the word as xystus, but used it to refer to a promenade in front of a portico, or an open colonnade or a walk flanked by trees. But they also took the Greek word for “polished” as a name – however, finding the /ks/ onset lacking in polish, they metathesized it to Sixtus, which was used as a name for six popes, the first of which was the sixth pope after Peter… and yet there is no link to the word six. (On the other hand, while John Paul II may have been the first Polish pope, there were six “polished” popes before him.)
This polished root has produced other words too: xyston, straight from the Greek, which, by reference to the polished shaft of a spear, referred to the spear itself; and xystum, an architectural term that can refer to any of several different things: a wall, a promenade, an alley, a path… seems kinda mixtup.
We brought the word xystus into English in the 1600s, and it’s still available as such; however, word collectors and Scrabble players will delight in having this clipped version available as well, just one of the little extra things English does for its players. If you’re going to wrestle with words, you might as well have good equipment to use – and a nice, polished place to do it, of course.
Do you have a vague feeling that there’s another word for “porch” or something similar that also has an x? There is: narthex, a vestibule in a church where (at least formerly) catechumens would stand. Perhaps if you put the two together, you would have a narthexyst. Oh dear, that rather looks like it’s had a collapse at the end, doesn’t it? Perhaps it’s what you get from wrestlers taking down the catechumens.