Clement of Alexandria says —Amarantus flos, symbolum est immortalitatis. The word is from the Greek amarantos (everlasting). So called because its flowers never fade like other flowers, but retain to the last much of their deep blood-red colour.
Milton: Paradise Lost iii. 353–61.Immortal amarant—a flower which once In Paradise, fast by the tree of life, Began to bloom; but soon, for man's offence, To heaven removed, where first it grew, there grows And flowers aloft, shading the fount of life... With these, that never fade, the spirits elect Bind their resplendent locks.
In 1653 Christina, Queen of Sweden, instituted the Order of the “Knights of the Amaranth,” but it ceased to exist at the death of the Queen. Among the ancients it was the symbol of immortality.
The best known species are “Love lies bleeding” (amarantus caudatus), and “Prince's feather” (amarantus hypochondriacus ). “Cock's comb” is now ranked under the genus Celosia.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894