So there's a Polish word "chmura", means a cloud but usually in a "raincloud" kinda deal, a darker cloud. And Russian from the same Proto-Slavic word has an adjective "хмурый" (hmuryj), which means "gloomy". Interestingly specifically "хмуриться", the verb form, means "knit one's brows". So kinda a "negative mood" word.
So from what I understand from reading about the origins of these words, the Russian word also initially meant "a gloomy cloud", which was via a metaphor transferred to mean a human mood, and then mostly got stuck at that meaning. You can still call various gloomy things "хмурый", but it's now making parallels to a gloomy mood and the cloud meaning is pretty much lost.