c. 1200, from Old English æmettig, of persons, "at leisure, not occupied; unmarried" (senses now obsolete), also, of receptacles, "containing nothing," of places, "unoccupied," from æmetta "leisure."
Watkins explains it as from Proto-Germanic *e-mot-ja-, with a prefix of uncertain meaning + Germanic *mot- "ability, leisure," possibly from PIE root *med- "take appropriate measures." A sense evolution from "at leisure" to "containing nothing, unoccupied" is found in several languages, such as 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 -p- is a euphonic insertion. Of words, etc., "destitute of force or effect," mid-14c. Related: Emptier. The figurative sense of empty-nester is attested by 1960.
Proto-Indo-European root meaning "take appropriate measures."
It forms all or part of: accommodate; accommodation; commode; commodious; commodity; empty; immoderate; immodest; Medea; medical; medicament; medicaster; medicate; medication; medicine; medico; medico-; meditate; meditation; Medusa; meet (adj.) "proper, fitting;" mete (v.) "to allot;" modal; mode; model; moderate; modern; modest; modicum; modify; modular; modulate; module; modulation; mold (n.1) "hollow shape;" mood (n.2) "grammatical form indicating the function of a verb;" must (v.); premeditate; premeditation; remedial; remediation; remedy.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit midiur "I judge, estimate;" Avestan vi-mad- "physician;" Greek mēdomai "be mindful of," medesthai "think about," medein "to rule," medon "ruler;" Latin meditari "think or reflect on, consider," modus "measure, manner," modestus "moderate," modernus "modern," mederi "to heal, give medical attention to, cure;" Irish miduir "judge;" Welsh meddwl "mind, thinking;" Gothic miton, Old English metan "to measure out."