The US liquid pint is a unit of volume in the US customary system with the symbol pt.
1 US liquid pint is equal to 1/8 US liquid gallon. This is equal to 1/2 US liquid quart, 2 US cups, 4 US gills or 16 US fluid ounces. The SI / metric equivalent is 473.1765 ml.
From the early (1707) adoption of the British wine gallon at 231 in³, the American pint was born. Where all pints are 1/8 of their respective unit system's gallon, that put the US pint at 28.875 in³.
The barrel is a unit of volume used in the oil industry with the symbol bbl.
Oil is more commonly expressed in terms of cubic metres (m³) but in the US and in the economic world (mainly because such a large percentage of the world's oil is shipped to the US) as barrels.
The measurement of the barrel originated in the US at the first oil well in Pennsylvania. There were so many variants of barrel size (including those used for wine and other goods) that the distrust became so prevalent a central and standard barrel size was created. This was finally established in 1872 as 42 US gallons.