also whippersnapper, 1670s, apparently a "jingling extension" [OED] of *whip-snapper "a cracker of whips," or perhaps an alteration of snipper-snapper (1580s). Compare also late 16c. whipperginnie, a term of abuse for a woman.
"A young and inexperienced person considered to be presumptuous or overconfident", Late 17th century: perhaps representing whipsnapper, expressing noise and unimportance.