It's where the word Marmalade comes from, lk.
Francis will correct me on this, I'm sure, but I have been reliably informed that Marmalade was originally made using Quince.
Wikipedia.....
http://en.wikipedia.org/wiki/Marmalade
"According to the Oxford English Dictionary, "marmalade" appeared in English in 1480, borrowed from French marmelade which, in turn, came from the Portuguese marmelada. Originally, according to the root of the word, which is marmelo or quince, a preserve made from quinces was intended....."
Citrus fruits were used at a later date.