organ of benevolence

I've never previously read A Christmas Carol. Happened across it in an iPhone edition recently, discovered that it's quite short (about 30,000 words—I had always assumed it was hundreds of pages), and started reading it. And I'm struck, as I was years ago when I finally read Oliver Twist, by the moments of charming humor.

I was also struck by a particular phrase when I came across it last night:

Old Fezziwig [...] rubbed his hands; adjusted his capacious waistcoat; laughed all over himself, from his shoes to his organ of benevolence; and called out in a comfortable, oily, rich, fat, jovial voice[....]

"Organ of benevolence" sounded like some kind of a euphemism, so I went and looked it up. Turns out it was one of the organs recognized by phrenology: it was "at the top of the forehead, near where the hair commences" (according to the Graham journal of health and longevity), and the size of one's organ of benevolence determined how benevolent one was (unless overridden by other factors, such as phrenology being meaningless).

My Google search also turned up a use of the phrase in Frederick Marryat's 1836 novel Mr. Midshipman Easy:

"Surely, sir, you would not interfere with the organ of benevolence."

"But indeed I must, Jack. I, myself, am suffering from my organ of benevolence being too large: I must reduce it, and then I shall be capable of greater things, shall not be so terrified by difficulties, shall overlook trifles, and only carry on great schemes for universal equality and the supreme rights of man. I have put myself into that machine every morning for two hours, for these last three months, and I feel now that I am daily losing a great portion."

Turns out Mr. Easy's invention pushes on or sucks on various parts of the skull in order to reshape the phrenological organs therein. I would call that science fiction, of a sort, but it was clearly presented as satire.