From Middle English lawe, laȝe, from Old English lagu, from Old Norse lǫg, originally the plural of lag, from Proto-Germanic *lagą, from Proto-Indo-European *legʰ-. Cognate with Icelandic lög, Swedish lag, Danish lov. Replaced Old English ǣ and ġesetnes. More at lay. Unrelated to French loi nor Spanish ley, since they both derive from *leǵ-.
From Middle English lawe, from Old English hlāw. Also spelled low.