Quicksilver

Quicksilver is the older name for mercury, from Old English, which dates from before 1150. It is mentioned in Chaucer, late 14th century. It has also been used in a figurative sense since the mid-16th century to describe quick motions, obviously an allusion to the quick motion of which the metal is capable. Today, it seems to be a favoured word among sports commentators to describe rapid moves.