v.
1. intr. (foll. by for) answer for, be surety for (will vouch for the truth of this; can vouch for him; could not vouch for his honesty).
2 tr. archaic cite as an authority.
3 tr. archaic confirm or uphold (a statement) by evidence or assertion.
Etymology: ME f. OF vo(u)cher summon etc., ult. f. L vocare call