That's how the mint labeled them in the rolls they sold. It's simply the order of release, i.e. Lincoln Penny 1, Lincoln Penny 2, etc.
Funny, last year someone told me it's properly called a Lincoln cent. I guess the U.S. Mint missed that memo. And FWIW, this is a 6-year-old thread.
Numismatically the correct term is CENT! However, in practical terms nearly everyone on the planet calls them "pennies". They are even labeled "pennies" on bank boxes and rolls. It's completely interchangeable IMO but if you collect them you should call them cents as a numismatist.