rejoinder (n.)

"to say in answer to a reply or later remark," mid-15c., a legal term, "answer a reply, reply a second time" (to a charge or complaint), from Old French rejoin-, stem of rejoindre "to answer to a legal charge," from Old French re- "back" (see re-) + joindre "to join, connect, unite," from Latin iungere "to join together, unite, yoke" (from nasalized form of PIE root *yeug- "to join").

"act of waiving," 1620s (modern usage is often short for waiver clause); from Anglo-French legal usage of infinitive as a noun (see waive). Baseball waivers is recorded from 1907. Other survivals of noun use of infinitives in Anglo-French legalese include disclaimer, merger, rejoinder, misnomer, ouster, retainer, attainder.

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."