Why does the King James have “turtle” in Song of Solomon 2:12?

Question

Ernie Harwell was famous for starting his first baseball broadcast of the Detroit Tigers spring with the following quote:

Song of Solomon 2:11-12 (KJV)
¹¹ For, lo, the winter is past, the rain is over and gone;
¹² The flowers appear on the earth; the time of the singing of birds is come, and the voice of the turtle is heard in our land;

It sounds funny to have a "turtle" pop up at the end of the quote, but I see that modern versions translate that word differently:

Song of Songs 2:11-12 (NIV)
¹¹ See! The winter is past;
   the rains are over and gone.
¹² Flowers appear on the earth;
   the season of singing has come,
the cooing of doves
   is heard in our land.

So how did the King James translators end up using "turtle" instead of some sort of bird?

Answer 1

Wiktionary claims turtle is an old word for dove (thus the term turtledove), derived from the Latin onomatopoeia turtur. Thus, in the language of the day, turtle did indicate the bird. See also Dictionary.com.