This line is an allusion to The Offering (2009), his fifth studio album.
The album artwork portrays Priest wearing a white robe with a crown right next to him, hence “hooded king”. It is a portrait of him and “portions” might refer to the servings of food on a dinner table.
This line shows the discrepancy between the seriousness of Aesop’s actions (cutting off a finger and mailing it to someone) with the desired outcome (a childish pinky swear).
The line also shows the futility of the gesture. He’s sending his thumb because he wants to be able to pinky swear. If he sent his pinky finger then he wouldn’t be able to do it.
The Dutch post-Impressionist painter Vincent van Gogh cut of his left ear while staying at a brothel in France in 1888. He wrapped the severed ear in newspaper and handed it to a prostitute named Rachel. Aesop also mentions this in the third verse.
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