This was originally published in my work Slack on 2016-10-04, but I’ve since been convinced that more people than just those few who can even read it there might be interested. I’ve edited it for clarity and correctness. I’m going to migrate all my Linguistcs Minutes over to my blog and probably post future ones here.

The modern word lay comes from a Proto-Germanic word *lagjan (the asterisk means it’s a reconstruction), which meant something like, “to put in place”. In Old English it also had the connotation of putting something down hard (“by striking”) in the form of lecgan.

The modern word law comes to us from Old English lagu of the same meaning as the modern word and was borrowed from Old Norse *lagu meaning “something that was laid down or fixed” which came from the Proto-Germanic word *lagam.

Both Proto-Germanic words come from a common Proto-Indo-Europoean root *legh- which meant “to lie down or lay”. So when you say you’re “laying down the law”, you’re sort of saying you’re laying down that which is laid down.