inkyoudaoicibaDictYouDict[ink 词源字典]
ink: [13] The Greeks had a method of painting which involved applying coloured wax to a surface and then fixing it with heat. The verb describing this process was egkaíein ‘burn in’, a compound of en- ‘in’ and kaíein ‘burn’, whose derivative egkaustikós is the ancestor of the term used for the technique in English – encaustic [17]. Another derivative, égkauston, was applied to the purple ink used by emperors in ancient times for signing documents.

As it passed via late Latin encaustum or encautum into Old French enque it gradually lost its imperial associations, and by the time it reached English as enke it was being used for any dark writing fluid.
=> caustic[ink etymology, ink origin, 英语词源]
ink (n.)youdaoicibaDictYouDict
"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.
ink (v.)youdaoicibaDictYouDict
"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.