Etymograph

English

key

Key comes from Middle English keye ‘a key’, and goes back to Proto-West Germanic *kaiju.

  1. Proto-West Germanicc. 200–500 CE*kaiju1reconstructed
  2. Old Englishc. 450–1150cǣġ2‘key’
  3. Middle Englishc. 1150–1500keye2‘a key’
  4. Englishearliest quotation 1613–1614key2

attested reconstructed ? uncertain or disputed deepest recorded ancestor

  1. 1 Wiktionary, Old English cæg
  2. 2 Wiktionary, English key, which cites Liberman
  3. Earliest quotation in Wiktionary’s entry: 1613–1614, John Fletcher, William Shak[e]speare: “2. Queen.[…]Deere Glasse of Ladies Bid him that we…”.

Lineage

  1. Proto-West Germanicc. 200–500 CE*kaijuWiktionary, Old English cægreconstructed
  2. Old Englishc. 450–1150cǣġWiktionary, English key, which cites Liberman‘key’
  3. Middle Englishc. 1150–1500keyeWiktionary, English key, which cites Liberman‘a key’
  4. Englishearliest quotation 1613–1614keyWiktionary, English key, which cites Liberman. Earliest quotation in Wiktionary’s entry: 1613–1614, John Fletcher, William Shak[e]speare: “2. Queen.[…]Deere Glasse of Ladies Bid him that we…”

The story

The only sure cognates are Saterland Frisian Koai (‘key’), West Frisian kaai (‘key’), and North Frisian kai, koie (‘key’). Possibly from Proto-Germanic *kēgaz, *kēguz (‘stake, post, pole’), from Proto-Indo-European *ǵogʰ-, *ǵegʰ-, *ǵegʰn- (‘branch, stake, bush’), which would make it cognate with Middle Low German kāk (‘whipping post, pillory’), and perhaps to Middle Dutch keige (‘javelin, spear’) and Middle Low German keie, keige (‘spear’). For the semantic development, note that medieval keys were simply long poles (ending in a hook) with which a crossbar obstructing a door from the inside could be removed from the outside, by lifting it through a hole in the door. Liberman has noted, however, "The original meaning of *kaig-jo- was presumably '*pin with a twisted end.' Words with the root *kai- followed by a consonant meaning 'crooked, bent; twisted' are common only in the North Germanic languages."

Full etymology on Wiktionary

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Another origin of key

  1. Taínomoderncayo‘small island’
  2. Spanishc. 1500–presentcayo‘key (island)’
  3. Englishtodaykey

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Today it means

noun An object designed to open and close a lock or to activate or deactivate something, especially a length of metal inserted into a narrow opening on the lock to which it is matched (keyed).

Sources

Sources: Wiktionary, “key”; the older steps come from the Wiktionary entry for Old English cæg. By Wiktionary contributors, CC BY-SA 4.0, via kaikki.org (dump of Oct 3 2026); text adapted and restructured. Language periods are conventional ranges, not dates for this word. License.

Etymograph / Proto-West Germanic *kaiju / key