Why do they call it pig iron ?  This shed view at the base of a blast furnace shows iron as it has been poured from the furnace into molds in a sand bed.
In early days the sand molds had small depressions that made the iron castings look like they had small feet.  Someone must have said they looked like pigs and the name stuck.

Postcard published by S.H. Kress, circa 1915.

Postcard Birmingham is a work always in progress by Warren Reed