corroborate (v.)

1520s, "to give (legal) confirmation to," from Latin corroboratus, past participle of 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 "to strengthen by evidence, to confirm" is from 1706. Sometimes 16c.-18c. in its literal Latin sense "make strong or add strength to," especially of medicines. Related: Corroborated; corroborating; corroborative.

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Definitions of corroborate from WordNet
corroborate (v.)
establish or strengthen as with new evidence or facts;
corroborate (v.)
give evidence for;
Synonyms: validate
corroborate (v.)
support with evidence or authority or make more certain or confirm;
Synonyms: underpin / bear out / support
corroborate (adj.)
serving to support or corroborate;
Synonyms: collateral / confirmative / confirming / confirmatory / corroboratory / substantiating / substantiative / validating / validatory / verificatory / verifying