www.alphadictionary.com

Halo

From Greek/Latin halos, signifying roundness: originally "threshing floor with a circular path", then "disk of the sun or moon", then "ring of light around the sun or moon", and finally (in English) "ring of light around the head".

There does not seem to be any connection with the Greek hals/halos meaning 'salt'.

I wonder if the circular bit is the actual threshing area, or the path the animals or people trod to turn the grinding stones.

This one's led me down a rabbit's hole of hal- words. Halo, halite, halitus, halitosis, hale, halyard, and further.