Jim Weirich once called it the “Very Good Suggestion of Demeter”.
In the article linked above, Martin Fowler is quoted with an even weaker formulation: the "Occasionally Useful Suggestion of Demeter".
They were very likely aware of each other. Jim Weirich said it in his talk The Grand Unified Theory of Software Development at Acts as Conference 2009, just a few weeks prior to the Fowler tweet.
Unusually, it's the kind of "law" that you are supposed to follow, not an observed law of nature.
It's mostly just a matter of usage, though in my personal (unwritten) style guide, 'law' would be reserved for constraints that, if not strictly true all the time, you generally cannot avoid (e.g. Moore's law), while a principle is a good idea that you would generally be well advised to try to conform to.
The definition of "principle" includes "law" - at least, according to the dictionary. I'm not sure I can identify a useful distinction in common use.
A principle is a personal choice to take or leave, to me. Law is imposed by the external world that doesn't defer to your opinion (but you can break it).