Correct. The original word is (w)orm, cognate to English wyrm (an archaic word for a dragon); the W sound in Scandinavian languages just vanished before back vowels like O a very, very long time ago (pre-Viking, even!).
Danish has been influenced by continental German, where a snake is of course a Schlange and a worm is a Wurm.
We have legendary "worms" in Britain, like the Lambton Worm, that are basically dragons, sometimes with a snakey aspect.
Smooth snake (Hasselsnok), Huggorm (European Viper/Adder) and Grass Snake (Snok/Gotlandssnok). I assume only as common as in the UK, and I have only ever seen one snake in the wild in the UK.
Yeah, it's kind of rare to see them, unless perhaps you're the hiking kind of person. I only ever once saw a huggorm and that was because it was dead... They're usually very shy.
unlike Indiana Jones, I love snakes, am a hiking kind of person, and will be in Sweden this summer. Hopefully, I see some.
I've only ever seen a Grass snake twice and an Adder once, though I'm not sure is a smooth snake is the same as a slow worm (which I once saw in a group of 3)
Smooth snakes and slow worms are not the same. Smooth snake (Coronella austriaca) is a snake, and is called "hasselsnok" in Swedish. The Slow Worm (Anguis fragilis) is a limbless lizard (not a true snake) and is called "kopparödla" or "ormslå" in Swedish.
Is "orm" etymologically a part of "jORMungand", or is it just a coincidence?