Doctor Johnson, being rowed down the Thames by a sculler, was assailed from the shore (as custom then was) by a foulmouthed fellow with a very generous flow of invective. Having endured as much as a man decently could, he turned on the scurrilist and said loudly and deliberately, “Sir, your mother, under pretext of keeping a bawdy house, was a receiver of stolen goods.” The subordinate clause provides at once the balance and the dynamic of this insult. “Under pretext of” gives evidence of judicious discrimination between appearance and reality; yet it implies that the man’s mother, casting about for the most decent front she could find for her fencing operations, could imagine nothing better than running a bawdy house. There is no way to make pretext or pretense of running a bawdy house except by running one, so that implication stands too. It is an extraordinarily opulent sentence; yet balanced, objective, and perfectly simple. One would like to think the recipient took it home and thought about it for several weeks.

— Robert Adams, Bad Mouth: Fugitive Papers on the Dark Side

In the course of my two minutes of Googling rigorous research, I learned that it was apparently considered good sport for boaters on the Thames to insult each other as they passed, but Adams suggests here that bystanders on the bank also took part. I find it much more amusing to imagine that some random weirdo just decided to verbally assault Johnson, whether he recognized him or not, just like I find it amusing to imagine a time-travelling Johnson taking part in a modern “Yo mama” fight. “Sir, it is a fact that your mother is so corpulent…”