Subconscious is derived from the Latin word, conscius, whereby con (root) means with, sci (root) means know, us (suffix) means tendency toward. Together, subconscious implies under the level of knowing. In psychology and social psychology, the word subconscious has come to be understood as a material sub-stratum that is not immediately accessible to consciousness. Pierre Janet (1859-1947), argued that underneath the layers of critical-thought functions of the conscious mind lay a powerful awareness that he called the subconscious mind.

Sigmund Freud first used the term "subconscious" in 1893 to describe associations and impulses that are not accessible to consciousness. He later abandoned the term in favor of unconscious, noting the following:

  • "If someone talks of subconsciousness, I cannot tell whether he means the term topographically – to indicate something lying in the mind beneath consciousness – or qualitatively – to indicate another consciousness, a subterranean one, as it were. He is probably not clear about any of it. The only trustworthy antithesis is between conscious and unconscious."

In 1896, in Letter 52, Freud introduced the stratification of mental processes, noting that memory-traces are occasionally re-arranged in accordance with new circumstances. In this theory, he differentiated between Wahrnehmungszeichen ("Indication of perception"), Unbewusstein ("the unconscious") and Vorbewusstein ("the Preconscious"). From this point forward, Freud no longer used the term "subconscious" because, in his opinion, it failed to differentiate whether content and the processing occurred in the unconscious or preconscious mind.

Carl Jung said that since there is a limit to what can be held in conscious focal awareness, an alternative storehouse of one's knowledge and prior experience is needed. This alternative storehouse is often referred to as the subconscious.

In the social sciences, the term subconscious, was resurrected in an article by Stajkovic, Locke, and Blair (2006) who referred to subconscious motivation as occurring "without intention, awareness, and conscious guidance." A review of early research on the subconscious can be found in Latham, Stajkovic, and Locke (2010)

Scholars have used other adjectives with similar meanings, such as unconscious, preconscious, and nonconscious, to describe mental processing without conscious awareness. The distinctions among these terms are subtle, but the term subconscious refers to both mental processing that occurs below awareness, such as the pushing up of unconscious content into consciousness, and to associations and content that reside below conscious awareness, but are capable of becoming conscious again.

Selecting one exclusive term presents theoretical tradeoffs, and empirical evidence does not yet exist to point exactly where the threshold of "below" or "without" consciousness is, because parts of the process are transitory.