calomel

UK: /ˈkæləˌmɛl/ US: (kal′ə mel′, -məl)

WordReference Random House Unabridged Dictionary of American English © 2025

cal•o•mel  (kal′ə mel′, -məl), n. [Pharm.]

1. Drugs a white, tasteless powder, Hg₂Cl₂, used chiefly as a purgative and fungicide. Also called mercurous chloride. 

• Neo-Latin calomelas coined from Greek kaló(s) fair + mélas black; allegedly so called because its original preparation involved turning black powder into white
• 1670–80

Collins Concise English Dictionary © HarperCollins Publishers::

calomel / ˈkæləˌmɛl -məl/ noun

1. a colourless tasteless powder consisting chiefly of mercurous chloride, used medicinally, esp as a cathartic. Formula: Hg₂Cl₂

Etymology: 17th Century: perhaps from New Latin calomelas (unattested), literally: beautiful black (perhaps so named because it was originally sublimed from a black mixture of mercury and mercuric chloride), from Greek kalos beautiful + melas black