I need help with this word from somebody who has a dictionary older than 1940.

In an old book I am reading, the writer bemoans the fact that critics hinder the enjoyment and appreciation of art.

The writer uses this sentence:

...I say, the critic, if he were or could be, as critic, to any degree a considerate human being, or graced by even the amenity of a Boojum, would "softly and silently vanish away." But critics, sadly, arent't like that. (emphasis mine)

I can't find a definition of Boojum that fits this sentence or what this man is trying to say.

I've found references to boojum trees and, as boojum being a particularly nasty snark, which is a creature invented by Lewis Carrol in 1951.

The book I am reading dates from 1939, so it definitely isn't the snark, and a boojum tree is rather rough and ragged and not anthing in which there would be amenities, so neither definitions fit.

I'm thinking it is a word that has fallen out of use or disappeared. It also seems a proper noun since it is capitalized.

Can anybody help?