existing or operating below the threshold of consciousness; being or employing stimuli insufficiently intense to produce a discrete sensation but often being or designed to be intense enough to influence the mental processes or the behavior of the individual:
1886, "below the threshold" (of consciousness), formed from sub "below" + L. limen (gen. liminis) "threshold." Apparently a loan-translation of Ger. 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.