Douglas Harper's Etymology Dictionary
Usage examples of "place-holder".
Duke, Vandros might like to have a few years to produce a ducal heir, and then perhaps a younger brother to take the earldom, and might choose to put in Mondegreen as Earl, as sort of a place-holder.
As her foot touches the plane, color flares from that point of contact, shoots out across the virtual floor, turning it from a mere place-holder to squares of brick and stone and lush beds of flowers.