Or amino acids. Many have a D (Dextrorotatory = right) or L (Levorotatory = left) form, indicating into which direction they rotate polarized light.

dexter is Latin for right and sinister is left, rotatory is probably rotation and hat fit in with polarization.

Where does levor... come from for left? Perhaps a newer Latin "left" than I was taught?

It comes from the Latin "laevus".

Funnily enough, although "sinister" came to mean "the bad side", it may have come from Proto-Indo-European for the "favourable side".

In politics in the UK, there is a left and right side of the "house". Currently the Conservatives are the right and Labour are the left. Neither party existed when the UK Parliament was initially created.

I wonder whether the old Latin (right == good/left == dodgy) thing has been perpetrated here or it it is coincidental.

I also wonder whether old Latin speakers really had a snag with sinister ie left handers or is that a modern affectation.

Knowing that ambidextrous thus means "both right (hands)" makes me marvel at how such a brazenly politically incorrect figure of speech has for so long remained undetected by the cultural police thanks to a linguistic camoflauge that mimics medical-sounding jargon.

The worst part is that up and down are not really opposites. Down is up on the other side of the world.

I'm not sure I follow you there. In that sense, "down" means toward the center of the gravity well. It is the same regardless of which side of the world you're on. If you mean that "down" changes direction with reference to a straight line, ok. But how does that make "up" not the opposite of it?

Up and down are opposites on the other side of the world too...

Up and down quarks have names that make perfect sense, they are derived from the isospin which in turn derives from spin (spin-1/2 was the only other well-known object in physics that had the same symmetry properties). Which one is up and which one is down is the only arbitrary choice.

Using "positive" and "negative" would have been a disaster. What charge does a positive antiquark have?