An Etymological Dictionary of Astronomy and Astrophysics

1. Something consisting of or regarded as having two parts or pieces joined together. → pair annihilation; → pair production.
   
2. Two identical, similar, or corresponding things.

Etymology (EN): M.E., from O.Fr. paire, from L. paria “equals,” neuter plural of par (genitive paris) “a pair, counterpart, equal.”

Etymology (PE): 1) Joft “pair, couple,” Lori, Laki jeft, Qâyeni jof, Tabari jeft, Mid.Pers. yuxt “pair, couple,” Av. yuxta- “a team of horses,” from yaog- “to yoke, harness, put to; to join, unite,” infinitive yuxta, Mid.Pers. jug, ayoxtan “to join, yoke,” Mod.Pers. yuq “yoke;” cf. Skt. yuga- “yoke,” Gk. zygon “yoke,” zeugnyanai “to join, unite,” L. jugare “to join,” from jugum “yoke,”
P.Gmc. *yukam, E. yoke; PIE *yeug- “to join.”
Hamâl, from ham- “together, with; same, equally, even” (Mid.Pers. ham-, like L. com- and Gk. syn- with neither of which it is cognate. O.Pers./Av. ham-, Skt. sam-; also O.Pers./Av. hama- “one and the same;” Skt. sama-; Gk. homos-; originally identical with PIE numeral *sam- “one,” from *som-. The Av. ham- appears in various forms: han- (before gutturals, palatals, dentals) and also hem-, hen-) + suffix -âl, → -al.