A binary large object, of course.

I expected most people here to know this. I've been proven wrong.

I had no idea. I thought it was just a fun word in the tradition of bits and bytes. It had an internal logic - you'd have datatypes for things, and then you had this catch-all amorphous type called the blob. It's a great name.

I would say it's even better if you omit "binary" even in the case you are not using an acronym.

Binary Large OBject