The people who said a food are the closest. It was a package of frozen ( formally frozen) peas. About two months ago my granddaughter had her wisdom teeth extracted and she got a dry socket and was in a lot of pain so my daughter gave her a package of frozen peas to use as an ice pack. Somehow it ended up under the bed and was forgotten. Lynda said the smell was so bad she didn't want to put it in the garbage can. Thanks for guessing or reading.