from
The Collaborative International Dictionary of English v.0.48
Calomel \Cal"o*mel\ (k[a^]l"[-o]*m[e^]l), n. [Gr. kalo`s
beautiful + me`las black. So called from its being white,
though made from a black mixture of mercury and corrosive
sublimate. Cf. F. calom['e]las.] (Chem.)
Mild chloride of mercury, {Hg2Cl2}, a heavy, white or
yellowish white substance, insoluble and tasteless, much used
in medicine as a mercurial and purgative; mercurous chloride.
It occurs native as the mineral {horn quicksilver}.
[1913 Webster]