Acceptors are elements added in the doping process that have one less electron in the valence shell than the substrate semiconductor material. With one less electron, this dopant “accepts” or pulls away an electron from the base semiconductor. By pulling away this extra electron, it creates a new “hole” in the semiconductor lattice. This creates a p-type semiconductor material.
Acceptors are trivalent impurity atoms that can take an electron. They are added during the doping process to create a p-type semiconductor.
Electronic Devices : Conventional Current Version, 9th Edition by Thomas L. Floyd
The diffused impurities with three valence electrons are called acceptor atoms.
Electronic Devices and Circuit Theory, 11th Edition by Robert L. Boylestad & Louis Nashelsky