To scrape the barrel is to use the worst things or people because nothing or no one else is available.
You chose Mark to represent us at the meeting? That's really scraping the barrel.
A: What are you wearing to the wedding?
B: The same dress as last time. I know I'm scraping the barrel. I just can't afford anything new!
If something is a barrel of laughs, it is funny or enjoyable. The phrase is often used in the negative form.
A: How was the meeting?
B: Pretty bad. We found out they are cutting 10 jobs. Not exactly a barrel of laughs.
A person who makes barrels is called a cooper. They also make other containers such as casks, buckets and tubs.