means In baseball, the player who throws the ball toward the batter from the mound to start each play; also, separately, a jug-like vessel with a handle and spout for pouring liquids.

from Two distinct words wearing the same coat. The vessel sense is the older traveler: it comes through Old French 'pichier' (a jug), from Medieval Latin 'picarium,' a cousin of the same family that gives us 'beaker.' The baseball sense is much younger and homegrown—simply 'one who pitches,' from the verb 'pitch,' meaning to throw or fling, attached to the 19th-century American game. So the man on the mound and the lemonade jug are linguistic strangers who happen to share a spelling.