Prep

google

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1920s: abbreviation of prepare or preparation.

etymonline

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prep (n.)

1862, short for preparation. Prep school is attested from 1895, short for preparatoryschool. First record of prep in the college slang sense "student or graduate of a preparatory school, student taking a preparatory course of study" is by 1899 (also see preppie).

prep (v.)

slang shortening of prepare, 1908. Related: Prepped; prepping.