I don’t think this has come up before. There’s an old piece where Cecil explains how come we ended up with salt and pepper; and apparently, back in the day, mustard was sometimes the default third condiment - though it really doesn’t have that status there days. I guess you see vinegar and ketchup more often these days (at least round these parts).
So: what should the third condiment be? The question is inspired by our recent discovery of Schoug (aka Schug, Skug, Zoug, Zhoug and half a dozen other names - Zhug - Wikipedia). It’s one of those foods which (a bit like pitta) crops up all over the middle/near East in related versions.
The version I know is definitely led by coriander (so possibly skhug yarok per wiki), and is made by an Israeli bakery (if you live in SE England, it’s Mamoosh in Newhaven). It has the remarkable property of going with, and enhancing, a remarkable range of things. At lunch today we were finishing things off - I had some cottage cheese, some hummus and some tuna pate: each was enhanced by (but not overpowered by) schoug. And that’s just a small sample of what it works with - hard cheeses, cold meats…
Actually, I do really like a good mustard, but I’ve changed my mind - for me, schoug is the third condiment. But I’ll certainly listen to other suggestions, and the reasons behind them…
The actual definition of condiment is news to me and in real world usage I would never considered salt or pepper condiments. They are seasonings to me.
Ketchup, mustard, hot sauce, relish, malt vinegar, good olive oil, chutney, Kimchi, mayonnaise … those are my standard pictured condiments.
Rarely add salt or pepper at the table myself. Hot sauce on occasion. Certain foods call for specific condiments of course, enough so that they are almost part of the dish and not really a condiment?
Back in my appraisal days we would occasionally (rarely) come across Victorian era shaker sets with three shakers. Two are obviously salt and pepper, the third is forgotten to time, possibly cinnamon or any number of other things. AFAIK, it’s never been successfully determined. The big one’s for salt.
Can we get a ruling from the OP… if you’re asking for a third condiment, what are the first two?
Salt and pepper, or ketchup and mustard?
(though Hot Sauce would be my vote for either scenario… I’ve seen diners here in the midwest with a little wire stand that holds napkins, salt, pepper, and hot sauce. Cholula, Frank’s, Sriracha seem to be the order of popularity with mom ‘n’ pop restaurant owners)