"the black liquor with which men write" [Johnson], mid-13c., from Old French encre, formerly enque "dark writing fluid" (11c.), originally enca, from Late Latin encaustum, from Greek enkauston "purple or red ink," used by the Roman emperors to sign documents, originally a neuter adjective form of enkaustos "burned in," from stem of enkaiein "to burn in," from en- "in" (see en-(1)) + kaiein "to burn" (see caustic). The word is from a Greek method of applying colored wax and fixing it with heat. The Old English word for it was simply blæc, literally "black." The -r- in the Latin word is excrescent. Donkin credits a Greek pronunciation, with the accent at the front of the word, for the French evolution; the same Latin word became inchiostro in Italian, encausto in Spanish. Ink-blot test attested from 1928.

"to mark or stain in ink," 1560s, from ink, n.. Meaning "to cover (a printing plate, etc.) with ink" is from 1727. Related: Inked; inking.