Because like I tell my daughter, by now we should know our right from our left:
- Right: اليَمين (al-yamīn), which comes from the same root as the country Yemen (اليَمَن), which archaically means “south” (reflecting a time when the compass was oriented to the east and the rising sun, putting south on the right)
- Left: اليَسار (al-yasār)
Arabic Word a Day 
Interesting. I didn’t know يمن meant south. Probably where they get شمال from which is the word for left/north, at least in Levantine colloquial…
That’s exactly right. شمال is “north” in MSA, but it has the older/archaic (and still colloquial) meaning of “left.”