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general::
Invigorate someone or cheer someone up, as in This drink will pep you up, or The good news about his recovery pepped us up. [1920s] Both the verb pep and the noun pep, denoting vigor and energy since about 1910, are abbreviations for pepper, a spice with a pungent, biting quality. They Also have given rise to pep rally, a meeting to inspire enthusiasm [c. 1940], and pep talk, a speech meant to instill enthusiasm or bolster morale [1920s].
American Heritage Idioms