1873, "below the threshold" (of consciousness or sensation), formed from Latin stem of sublime (Latin limen, genitive liminis) + -al (1)). Apparently a loan-translation of German unter der Schwelle (des Bewusstseins) "beneath the threshold (of consciousness)," from Johann Friedrich Herbart (1776-1841), author of a textbook on psychology published in 1824. The scare over subliminal advertising came in 1957. Related: Subliminally.
