on one's toes

on one's toes

Alert, ready to act, as in Orchestra players must be on their toes all the time, so as not to miss an entrance. This metaphoric expression probably alludes to boxers or runners who must be on their toes in order to move or start quickly. It gained currency with Richard Rodgers' and Lorenz Hart's extremely popular musical, On Your Toes (1936). [Early 1900s]
See also: on, toe