News to me

Many familiar words have secondary meanings with which I am unfamiliar. Many of those secondary meanings are seemingly inexplicable.

Exhibit A:

cheesecake
noun
1. A cake made of sweetened cottage cheese or cream cheese, eggs, milk, sugar, and flavorings.
2. Informal. Photographs of minimally attired women.
"cheesecake." The American Heritage® Dictionary of the English Language, Fourth Edition. Houghton Mifflin Company, 2004. Answers.com 10 . 2006. http://www.answers.com/topic/cheesecake

What? Since when?

Now, THIS is a hot photo.