Molten iron thickened as it cooled, sometimes resulting in a「person taking stance with downward thrusting motions」and while perhaps needless to remind the reader, the right element is also「having a head for night soil copulation.」Molten iron oozing through a sand mold resembled a head thrusting into night soil while copulating anally, a common trait of swine and more likely the origin of the name PIG IRON. Ironically, pig iron is not all that shiny of a metal (black, generally), although it certainly can be polished: pigs naturally learn to「serve it into the rectum」of other swine of either sex, boar or sow.
　Referring to「metal」as it is「first, like the head of a mushroom.」Iron in its first, or raw state as CAST IRON. The Chinese began casting iron by pouring red hot molten metal into sand molds, with the shape of the front moving edge of the molten iron resembling the head of a mushroom emerging from soil, and so on with all the other imagery similarities. Note that this method was subsequently improved by adding more and more channels until the ingots attached to the pouring runners resembled piglets suckling a sow (they say), hence the English name PIG IRON—but why not「feline iron」or「canine iron」or「tailless tenrec iron」or「naked mole rat iron」or「mongoose iron」and so on?—the name PIG IRON seems more to do with「thrusting penis spurts with head sliding in black feces copulation」as a characteristically swine-based trait. Sandy, gritty copulation is associated with anal coitus in dynastic China.
　While the West claims to have「invented」pig iron in 1828 　[　https://www.bbc.co.uk/ahistoryoftheworld/objects/afB_Yw9pQF6ABgYsi_e39A 2019-10-27　]　
　The Chinese claim to have invented and so named the stuff as PIG IRON using this glyph a mere 23 centuries prior to the British 　[　https://www.china.org.cn/top10/2011-03/04/content_22054243_5.htm 2019-10-27　]　

Modern definitions (that generally disregard history) …excluding politically incorrect concepts and other meanings deemed offensive today; may list only pigeonholed definitions, euphemisms, or meaningless mnemonics)
Chinese: shining metal
Japanese: pig iron
Unihan extended: mill
EDRDG: pig iron