Dotard
Definition: someone exhibiting mental decline in old age
The origin of this goes back to “dote,” which is Old English for “to act foolishly.” This is where we get the verb form of “to dote,” which means to lavish foolish levels of attention on someone.
It’s also where we get “dotage,” which is someone’s old age where they experience mental decline (presumably: become like a fool).
Finally, we arrive at “dotard,” which is the noun form, meaning a person who is in that stage of life.
Why I Looked It Up
I didn’t note the book, but I wrote down the quote:
[…] viewing them as nine dotards in robes.
From context, I’m assuming this was something about the Supreme Court.
Postscript
Added on
I saw a Reddit thread entitled:
Hoisted by their own dotard
This is a play on “hoisted by their own petard.”