Synonyms for Corroborate (same or very similar meaning)
WordNet sense 1 (support with evidence or authority or make more certain or confirm):
support, underpin, bear out
WordNet sense 2 (give evidence for):
validate
WordNet sense 3 (establish or strengthen as with new evidence or facts):
affirm, confirm, substantiate, sustain
From the ODE community, based on WordNet
add/edit