Proto-Indo-European root meaning "to join."
It forms all or part of: adjoin; adjust; conjoin; conjugal; conjugate; conjugation; conjunct; disjointed; enjoin; injunction; jugular; jostle; joust; join; joinder; joint; jointure; junction; juncture; junta; juxtapose; juxtaposition; rejoin (v.2) "to answer;" rejoinder; subjoin; subjugate; subjugation; subjunctive; syzygy; yoga; yoke; zeugma; zygoma; zygomatic; zygote.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit yugam "yoke," yunjati "binds, harnesses," yogah "union;" Hittite yugan "yoke;" Greek zygon "yoke," zeugnyanai "to join, unite;" Latin iungere "to join," iugum "yoke;" Old Church Slavonic igo, Old Welsh iou "yoke;" Lithuanian jungas "yoke," jungti "to fasten to a yoke;" Old English geoc "yoke."
1520s, "title given to a widow of rank to distinguish her from the wife of her husband's heir bearing the same name," from French douagere "widow with a dower" literally "pertaining to a dower," from douage "dower," from douer "endow," from Latin dotare, from dos (genitive dotis) "marriage portion, dowry" (from PIE *do-ti, from root *do- "to give").
"App. first used of Mary Tudor, widow of Louis XII; then of Catherine of Arragon, styled 'Princess Dowager'" [OED]. In law, "a widow possessed of a jointure."