It looks like plastic, and it's not a drain plug. I, too, think it's something from the end of a metal or plastic broom handle or similar, there so you can hang the tool up if you wish.
It's not a drain plug, they have hex heads for socket/wrench to turn. Does the loop rotate or fold down? I've never seen anything like that, worked 2 years in a hardware store in high school and have been working on cars since I was 15 (16+ years now).
Almost looks like a drain plug for the oil pan.
How about the tip of a broom handle?
It looks like a chain retainer for a chandelier. The hole is for the wire to go through, here is a picture of something similar:
I found this nut on the floor of my garage under the car. I do not know if it fell out of the car or that it may belong to something else. Can anyone help?
