1798, "common hemp," from Cannabis, Modern Latin plant genus named (1728), from Greek kannabis "hemp," a Scythian or Thracian word. Also source of Armenian kanap', Albanian kanep, Russian konoplja, Persian kanab, Lithuanian kanapės "hemp," and English canvas and possibly hemp. In reference to use of the plant parts as an intoxicant, from 1848. Related: Cannabic.
Latin adjectives in -aceus sometimes were made in Romanic languages into nouns of augmentative or pejorative force. Especially as a surface for oil paintings from c. 1700; hence "an oil painting" (1764).