I'm Brazilian, a zennial, and I have a similar freckle on the other side of my left arm, as well as another freckle on the same spot, on my right arm tho. Is it related to some vaccine shot from childhood, or other factor? (I remember having some shot mark from one of these shots over the upper arm, dunno which shot, if parotitis or rubella)
At least in the USA, it's probably due to having been alive long enough for sun damage to cause a freckle on the side of your body nearest the car window while driving.
I'm a pretty heavily freckled person, but damn if I don't have a pronounced, solitary freckle precisely at this location on my left arm.
I bet it's related to driving with my left arm hanging out the window. In the US at least, people who do that have their left arm over-exposed to sun damage.
I've gotten suuuper into introspective / therapeutic tarot reading and in my related research I've come across a bunch of techniques used by people who use them performatively as a divinatory illusion. The funniest part is if I was going to do it therapeutically for another person I would probably do all the same things I'd just be honest that that was what I was doing. Kinda like a ritualistic / spiritually themed rorschach test.