Sense of to exist, be present is attested from c.1300. Meaning to pay for as a treat is from 1821. Phrase stands to reason (1620) is from earlier stands (is constant) with reason. Phrase stand pat is originally from poker (1882); stand down in.
In Expert Mode, Wall of Flesh is seen to be significantly faster than his prior speed, posing map navigating harder as the players are demanded to plan out their routes fasters. In addition, getting pulled by his tongue will inflict additional damage to the player, possibly killing a weakened player.
Loot & Hard Mode. The Wall of Flesh will explode, leaving behind a box that you can mine into in order to get your loot. This is to protect the loot from falling into lava. The 100% drop is the Pwnhammer, which is used to break Demon Altars to bless your world with new ore types.