I think of barrels as wooden, assembled from curved "staves," giving the barrel a "bulging" shape. I think of Budweiser being "beechwood aged" in such barrels. The famous polka, "Roll Out the Barrel" refers to a barrel of beer being rolled across the floor at a dance.
Going back even before my time, some food items such as pickles were sold in bulk from barrels in the store. You still hear the expression, "cash on the barrel head."
Of course these days the most famous barrel is a barrel of oil, which is actually just a unit of measure.
Everything is now made of plastic, as your referenced pictures show.
Best wishes, - A.
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I believe this is a drum then. Avangi, are those the two ridges you are talking about? By the way, is groove the opposite of ridge?
I agree with Avangi on this one