On Sat, 20 Apr 1996, The Tendo Basement wrote:

By-the-by: Does anybody know why a Lemon fic is called a lemon?

Because it started with something called "Cream Lemon?"  I don't know!

That's what I've heard - that the term "lemon" comes from the very 
lemon-y anime "Cream and Lemon."

-joyce, Disciple of Kasumi
who has NEVER seen Cream and Lemon and NEVER plans to
Joey-kun no iinzuke!