English

Noun

caput mortuum ‎(uncountable)

1. worthless residue, useless substance
2. Cardinal purple, a variety of haematite iron oxide pigment

Latin

Etymology

Collocation of caput + mortuum, literally "dead head". Figurative use from alchemical literature.

Noun

caput mortuum

1. a dead man's head, a skull
2. worthless residue, useless substance
   • 1591 "Caput mortuum, ut est apud Paracelsum, sign. materias, quae sunt in fundo vasis chimici" (Antonio Ricciardo, Commentaria symbolica, p. 138)
3. Cardinal purple, a variety of haematite iron oxide pigment