Where did DISC come from?

DISC is a four quadrant behavioral model, based on the work of William Moulton Marston PhD (1893–1947), that examines the behavior of individuals in their environment or within a specific situation.  The model first looked at how people perceived their environment (favorable or unfavorable) and how they perceived themselves in the environment (whether they had control or no control).  The four combinations make up the four DISC Styles.

High Dominant people believe the environment is generally UNFAVORABLE but they believe they have CONTROL over it.
(Subsequent traits: aggressive, bold, competitive)

High Influence people believe the environment is generally FAVORABLE and they believe they have CONTROL over it.
(Subsequent traits: optimistic, friendly, confident)

High Steadiness people believe the environment is generally FAVORABLE but they believe they have NO CONTROL over it.
(Subsequent traits: shy, passive, deliberate)

High Compliant people believe the environment is generally UNFAVORABLE and they believe they have NO CONTROL over it.
(Subsequent traits: cautious, analytical, detail-oriented)

As you can see, knowing how people perceive their environment and themselves in it is extremely useful in understanding their behavior.
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