According to the company's web site:
The wood in your floors comes from the great brewing vats, ... each capable of holding some 722,600 pints of stout. Brown oak was used because it had the strength and grain to handle the stress of the process. Knots, which could give way, were filled with tiny hand carved wedges tapped in for extra strength. Many of those details were saved and can still be found in the wood.
In the late 1900's Guinness® replaced the wooden vats with metal. Some were stored and rescued by Mountain Lumber. We were able to import more than 100,000 board feet of 100-year-old oak staves. That wood was kiln dried, re-milled and transformed into the wonderful European Cooper's Oak™ you now enjoy.
Now, if I ever get around to finishing off the basement, this would make an interesting addition.