The evidence against the Swedish explanation is that the ball says c for 'cat' and d for 'dog', but in swedish the translations are 'katt' and 'hund' respectively.
This may be a case where the most upvoted answer is likely wrong, but because it was so entertaining and took so much effort, it was upvoted much more than the boring (but probably correct) answer.
EDIT: I had only skimmed the most upvoted answer, it does indeed trace the ball's manufacture to China and suggest the 'y for axe' is a typo. Apologies for the confusion.