cyanide (n.)

word-forming element used in science for the carbon-nitrogen compound radical, from a Latinized form of Greek kyanos "dark blue" (see cyan).

The immediate source of its use in science is French cyanogène, the name given to the compound radical by Gay-Lussac. He called it that because it first had been obtained by heating the dye pigment powder known as Prussian blue (see Prussian).

The cyanogen radical was one of the first examples of a 'compound radical' and was of importance in the development of structural chemistry during the next forty years. [Flood, "Origins of Chemical Names"]  

word-forming element used in chemistry to coin names for simple compounds of one element with another element or radical; originally abstracted from oxide, which was the first so classified, in which the -ide is from acide "acid."

The suffix is really -dus (-do-), the -i- repr. the orig. or supplied stem-vowel ; it occurs without the vowel in absurdus, absurd, blandus, bland, crudus, raw (crude), etc. [Century Dictionary]

"compound of chlorine and another element," 1812, coined by Sir Humphry Davy from chlorine + -ide on the analogy of oxide.