Douglas Harper's Etymology Dictionary
halo-
before vowels hal-, word-forming element meaning "salt, sea," from Greek hals (genitive halos) "a lump of salt, salt generally," in Homer, "the sea," from PIE *sal- "salt" (see salt (n.)).
Wiktionary
halo-
Etymology 1 pre. Forming compound words with the sense of ‘sea, salt, salt water’. Etymology 2
pre. (context chemistry English) Forming names of chemical compounds which contain one or more halogen atoms.
Wikipedia
Halo-
Halo- is a Greek prefix meaning " salt." In biology, it is often used to indicate halotolerance and is a portion of many words:
- Halobacteria
- Haloclasty
- Halophile
- Halophyte