Earlier I wrote about the “his/he’s” distinction in Singapore, which corresponds to the “ship/sheep” distinction this pronunciation book refers to.
Apparently people have been struggling to differentiate these two words at least since the time of George Eliot. This is a passage from Middlemarch, published in 1872.
“I hate grammar. What’s the use of it?”
“To teach you to speak and write correctly, so that you can be understood,” said Mrs. Garth, with severe precision.
“Should you like to speak as old Job does?”
“Yes,” said Ben, stoutly; “it’s funnier. He says, ‘Yo goo’—that’s just as good as ‘You go.'”
“But he says, ‘A ship’s in the garden,’ instead of ‘a sheep,'” said Letty, with an air of superiority. “You might think he meant a ship off the sea.”
Here’s a more modern take: a pun that requires the conflation of “Griddy” (the name of an F&B outlet at Our Tampines Hub) and “greedy”: