give supporting evidence; "He vouched his words by his deeds" summon (a vouchee) into court to warrant or defend a title give personal assurance; guarantee; "Will he vouch for me?
If you say that you can vouch for something, you mean that you have evidence from your own personal experience that it is true or correct. He cannot vouch for the accuracy of the story
If you say that you can or will vouch for someone, you mean that you can guarantee their good behaviour. Kim's mother agreed to vouch for Maria and get her a job