From sun and odino; to have (parturition) pangs in company (concert, simultaneously) with, i.e. (figuratively) to sympathize (in expectation of relief from suffering) -- travail in pain together.
see GREEK sun
see GREEK odino
a. properly, to feel the pains of travail with, be in travail together: οἶδε ἐπί τῶν ζοωον τάς ὠδῖνας ὁ σύνοικος καί συνωδίνει γέ τά πολλά ὥσπερ καί ἀλεκτρυονες, Porphyry, de abstin. 3, 10; (cf. Aristotle, eth. Eud. 7, 6, p. 1240a, 36).
b. metaphorically, to undergo agony (like a woman in childbirth) along with: Romans 8:22 (where σύν refers to the several parts of which ἡ κτίσις consists, cf. Meyer at the passage); κακοῖς, Euripides, Hel. 727.