Look at this word: it looks like a long bridge, with two piers – perhaps two double piers. It has a nice visual rhythm to match the rhythm of saying it. It starts with the lips out, then they bounce together, then you go to the tongue tip, then the lips again; the vowels match, with a higher forward /ɪ/ to go with the forward /w/, and a lower /æ/ to go with the pulled-back /sn/, and in the off syllables bouncing from /p/ you have that syllabic /ɹ/ with the tongue bunched up in the middle. If you say the wh as /hw/ then you have a voiceless consonant at the start of every syllable, giving it an appealing contrast and crispness – but even without that touch, it still cracks.
Cracks like a whip? Perhaps, or should we say snaps like one. After all, that’s where this word seems to come from: whip-snapper, extended for the echo and rhythm in a similar way to fixer-upper and quicker picker upper. But what has this to do with what the word refers to? Its object might seem to be more like a wimpy little whippoorwill of a person, or at most an impertinent pipsqueak. Look at what the word most often goes with: young whippersnapper (and you can hear a creaky old man’s voice saying it, can’t you?). Sometimes it’s little whippersnapper. You wouldn’t expect such a snippet to snap a whip at anyone.
But that’s just the point: this insignificant personage is attempting to order around his (or her) superiors, or, by extension, to behave towards them as though they were inferiors. (It is possible, however, that the word was first a word for a ruffian of whatever age and size, and that it subsequently narrowed to refer to rambunctious youth, and shifted to indicate impertinence rather than violence.)
Whippersnappers have of course been around from the dawn of time: impertinence is a characteristic of youth, and resentment of the impertinence of youth is common for some types of older people. Interactions that would give occasion to use the word whippersnapper can be found in comedies throughout the ages. The word whippersnapper, however, dates only from the later 1600s.
What did they call them before that? Hm. The options are plenty. I immediately hear John Gielgud’s voice: “You little shit.”
Thanks to Margaret Gibbs for suggesting whippersnapper.