The caramelized food bits left at the bottom of the pan.
The culinary food term, French for "base" or "foundation."
But you would not say "my fond hurts," even if you were French.
Or, "you're being a real pain in my fond."
Is it an expression of endearment? Yes. Ex: M. Arbuthnot was very fond of dogs.
He once was not fond of dogs because he'd been bitten by a terrier as a child, but now he is. He owns terriers. It's the kind of a transformation that happens sometimes in the best fiction, but rarely in real life.
It's a pan sauce made with the dried up caramelized dark bits of the past. Yet it is the beginning of something new.
And so what are you cooking?