Why is the ninth month called September?
c.1200, from Old English æmettig "at leisure, not occupied, unmarried," from æmetta "leisure," from æ "not" + -metta, from motan "to have" (see might (n.)). The -p- is a euphonic insertion.
Sense evolution from "at leisure" to "empty" is paralleled in several languages, e.g. Modern Greek adeios "empty," originally "freedom from fear," from deios "fear." "The adj. adeios must have been applied first to persons who enjoyed freedom from duties, leisure, and so were unoccupied, whence it was extended to objects that were unoccupied" [Buck].
The adjective also yielded a verb (1520s), replacing Middle English empten, from Old English geæmtigian. Related: Emptied; emptying. Figurative sense of empty-nester first attested 1987. Empty-handed attested from 1610s.
in mysticism and religion, a state of "pure consciousness" in which the mind has been emptied of all particular objects and images; also, the undifferentiated reality (a world without distinctions and multiplicity) or quality of reality that the emptied mind reflects or manifests. The concept, with a subjective or objective reference (sometimes the two are identified), has figured prominently in mystical thought in many historical periods and parts of the world. The emptying of the mind and the attainment of an undifferentiated unity is a theme that runs through mystical literature from the Upanisads (ancient Indian meditative treatises) to medieval and modern Western mystical works. The concepts of hsu (q.v.) in Taoism, sunyata (q.v.) in Mahayana Buddhism, and the En Sof in Jewish mysticism are pertinent examples of "emptiness," or "holy Nothing," doctrines. Buddhism, with its basic religious ultimate of Nirvana (q.v.), as well as its development of the sunyata doctrine, has probably articulated emptiness more fully than any other religious tradition; it has also affected some modern Western considerations of the concept. A good deal of 19th-20th century Western imaginative literature has been concerned with emptiness, as has a certain type of Existentialist philosophy and some forms of the Death of God movement. The particular meanings of "emptiness" vary with the particular context and the religious or cultural tradition in which it is used.