You’d simply carve the names of all potential suitors into some pieces of cheese, then wait to see which one molded first. And there it was—your life partner!
Eating the results won't always be a fun time, but I suppose there's bond to be risks when trying to change your fate.
Wait, tyromancy is real?! I thought CDPR were joking when they made an entire quest line out of it in the Witcher 3. I got a nice sword called the Emmentaler out of it and everything. Huh. TIL indeed. Thanks, OP. I never thought to Google it.
The art of telling your future by reading your butt. Invented by...
You guessed it, Sylvester Stallone's late mother : Jackie Stallone.
( Or the ancient Babylonians as she'd claim)
Or you can use Chicken Box from McDonald's™ to predict someone's future. What you do is to tell them to buy largest Chicken Box and bring it, then predict future by reading how the nuggets look, how they are assembled in the box, what sauces the client chosen, how they taste, take your time with that last one, really get in there, try them all, that would be 50 dollars.
Well, if you want to really stretch that out into something that would make sense, despite still being utterly ridiculous, follow along.
So, we all have our own micro-biome. We're literally crawling all over, inside and out with bacteria, fungi, and teeny tiny little mites, plus whatever else I'm forgetting.
The exact balance of those influences our health, mental and physical. Imbalances can cause anything from a yeast infection or bacterial vaginosis all the way up to death. There's possibilities where it can be related to things like Alzheimer's, MS, etc, all kinds of diseases and disorders where it isn't the cause, but it can change exactly how things go.
When two people spend a lot of time in close contact, their personal micro-biomes mix up. That's one of the reasons that new sexual partners of the hetero persuasion often end up with fresh yeast infections and/or bacterial vaginosis. The contact throws things out of whack, and it takes time to reach balance again.
So, if you want to pretend it isn't bat-shit crazy, the name that molds first is because you likely spent more time in contact with that person before carving their name, since you wouldn't be using their name if you aren't interested in the first place. So, you end up carving the name of the person you want to be yours, which transfers the mold on your hands the most.
And, since you've had that extended contact, they're a better match because you've already started sharing microorganisms!
Boom! Science, bitches! (For a given value of actual science, where that value is somewhere above zero, but only to a degree detectable with advanced microscopy)