How about/how do you like them apples?

American expressions of delight and triumph, usually inviting admiration or praise for something one has achieved or acquired, rather than a reply. Sometimes, onions or potatoes are used instead of apples for no apparent reason. It first dates from c. 1940 and its origin is unknown but it is thought to be an embellishment (for added emphasis?) of the much more common, how about that? Or how about that then? Which are both from earlier in the 20th century.