English
invisible ink
From invisible + ink.
Proto-Indo-European *weyd- ‘to see’
…
Latin vīsibilis ‘that may be seen, visible’
Late Latin invīsibilis
Old French invisible
Middle English invisible
English invisible
Ancient Greek ἔγκαυστον ‘burned-in’
Latin encaustum ‘purple ink used by Roman emperors to sign…’
Old French enque
Middle English ynke
English ink
Today it means
noun An ink, invisible on application or soon thereafter, that can later be rendered visible by some process, such as exposing it to heat.
Language periods are conventional ranges, not dates for this word.
Etymograph / invisible ink