"the black liquor with which men write" [Johnson], c.1250, from O.Fr.
enque "dark writing fluid," from L.L.
encaustum, from Gk.
enkauston "purple or red ink," used by the Roman emperors to sign documents, originally a neut. adj. form of
enkaustos "burned in," from stem of
enkaiein "to burn in," from
en- "in" +
kaiein "to burn" (see
caustic). The word is from a Gk. method of applying colored wax and fixing it with heat. The verb meaning "to mark or stain in ink" is from 1562.
Inky "as black as ink" is attested from 1593.
[ingk] 
