In Arthur Ransome's Coot Club (1934), the Hullabaloos are the "bad guys": obnoxious tourists, three men and two women, who roar around the inland waters of the Norfolk Broads in a rented powerboat, blaring popular music and generating a bow wake that threatens to swamp small craft belonging to locals.
Their behavior also threatens nesting water birds.
The male Hullabaloos grab a local boy, Joe, by the coat, accusing him of something he did not do. Joe wriggles out of his coat. After a local policeman intervenes and refutes the accusation, Joe is no longer under threat. On page 92 of the 1990 edition (David R. Godine):
"And my coat?" said Joe.
He came warily forward and picked it up, put it carefully on and then pulled out of an inner pocket a large white rat, which sat on his arm, sniffed the air contemptuously, and looked about it with its round pink eyes.
"Take that thing away," screamed the woman.
"Now then, 'Livy. You don't mind that. Not wearing skirts...." The fat man of the three stopped suddenly as the woman in orange trousers gave him a resounding slap in the face.
This seems to allude to a folk belief, joke, saying, or men's obscene suggestion, about rats and skirts.
Perhaps the fat man means: "You don't have to worry about the rat running up your leg and threatening your private parts, because you're wearing pants."
First, in 1934 would a middle-class female English tourist wear pants while vacationing on an inland power boat?
For purposes of literary interpretation, I think we can disregard the technical question of whether a rat would just as soon run up a man's pants as up a woman's skirt.
The fact that a British newspaper published the following story from New York suggests that the idea has salacious tabloid-style appeal: Daily Mail, 11 June 2012. The same incident appears a day later in the USA: New York Daily News, 12 June 2012.
But is there some specific item of folklore, prevalent in 1930s Britain, to which the fat man alludes?