Comment by xandrius
2 hours ago
The first example is not really a coincidence: a second is defined by being the second subvision of an hour.
So that example fails to support any reason for akari matching light in English. But for the sake of argument here is another one: じゃり (giari, read as "ja-ri") in Japanese means gravel and in my dialect almost the same sound (giarin, "ja-ri-n") also mean gravel. Go figure.
That was exactly my intended point (and my comment does mention the hour subdivision). There are a lot of meaningless coincidental homonyms, but these tend to not be homonyms in other languages. E.g. I dunno "left" in English would be "izquierda" or "dejó". Or conversely, "vino" in Spanish would be "wine" or "came". The fact that "second" and "segundo" have homonyms in their respective languages is a clue that the unit of time and the ordinal word are the same is not a coincidence. And when you look into it it's for the reason that you state. The homonym pairs indicates an etymological relationship between the two concepts.
So I was wondering if the same applied here. My initial reaction is that "light" meaning "illuminated" and "light" meaning "not heavy" is that this is just one of those coincidences, since I can't see how that one word relates the two concepts. But given that Japanese also does the same, it makes me wonder if maybe there is some sort of relationship. Maybe it was a common belief historically that the sun was not very heavy or something like that. Or maybe not and it's just a rare double coincidence!