1667, "frightening," from L. terrificus "causing terror or fear," from terrere "fill with fear" (see terrible) + root of facere "to make" (see factitious). Weakened sensed of "very great, severe" (e.g. terrific headache) appeared 1809; colloquial sense of "excellent" began 1888.
mod. excellent. : Glad to hear it. That's just terrific.
Dictionary of American Slang and Colloquial Expressions by Richard A. Spears.Fourth Edition. Copyright 2007. Published by McGraw Hill.
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