- \ \ Caper ‘jump about’  and the edible caper  are two different words. The former is a shortening of capriole ‘leap’, now obsolete except as a technical term in horsemanship, which comes via early French capriole from Italian capriola, a derivative of the verb capriolare ‘leap’, which in turn was formed from capriolo ‘roebuck’; its ultimate source was Latin capreolus, a diminutive form of caper ‘goat’ (whence the English astrological term Capricorn, literally ‘goat’s horn’). (The French by-form cabrioler was the source of English cab.) Caper ‘edible bud’ came via French câpres and Latin capparis from Greek kápparis; the earliest English form was capres, but this came to be misinterpreted as a plural, and the -s was dropped from the singular in the 16th century.\ \ Cf.⇒ CAB, CAPRICORN, CAPRIOLE
Word origins - 2ed. J. Ayto. 2005.