My Dad loved reading the classics, and he used to lecture us about ancient societies. (My more pragmatic Mom dismissively referred to his beloved ancients as "those old Greeks.")
One day I while I was reading, I came across the word plebeian and asked Dad the meaning.
Apparently it was the question he'd been waiting for. He went on and on, lecturing me on the social classes of ancient Rome, the patricians and plebeians.
Then he explained about the contemporary connotation of the word plebeian, its association with vulgarity and ignorance.
I latched onto that immediately. Whenever my siblings said or did something less than classy, I would look down my nose and remark, "How plebeian."
They retaliated by stealing my term and applying it to me. For a few months, the favoured mode of criticism around our house was to say in a haughty tone, "How plebeian."