corroboration (n.)

mid-15c., corroboracioun, "act of strengthening, support" (a sense now obsolete), from Late Latin corroborationem (nominative corroboratio), noun of action from past-participle stem of Latin corroborare "to strengthen, invigorate," from assimilated form of com "with, together," here perhaps "thoroughly" (see com-) + roborare "to make strong," from robur, robus "strength," (see robust). Meaning "act of confirming, verification, confirmation" is attested by 1768.