Could be often worn clothing that smells. I had 2 bras I wore everyday and over time they absorbed sweat and deodorant so much it would not come out clean no matter how many times or how they were washed. Took me a while to figure that one out and they got tossed. It can happen with anything you wear a lot. Also, it could be the washing machine. Sometimes they can get mildewy or gunk can build up in the hoses and transfer the smell to clothing. Front loading washing machines are known for that off stink if not aired properly. It could even be shoes that have absorbed smells and are giving out a peculiar odour. My school shoes in high school stank to high heaven. I sprayed them with glen 20 antibacterial and they reeked of that old person scent forever after, at least until I tossed them (triple bagged and I could still smell it ugh) Febreeze or odour eaters did zilch.
It's surprising what can stink.