Just Wondering

Just wondering:

• If you put the words " the IRS" together you get a new word--theirs.
• When cows laugh, does milk come out their noses?
• We call a device used to walk about and talk a walkie-talkie, so why isn't a vacuum cleaner called a pushy sucky?
• Why is the word abbreviate so long when it means a shortened version of a word?

Like I said, just wondering.