voucher

n. 1. One who vouches, or gives witness or full attestation, to anything. [ 1913 Webster ]

Will his vouchers vouch him no more? Shak. [ 1913 Webster ]

The great writers of that age stand up together as vouchers for one another's reputation. Spectator. [ 1913 Webster ]

2. A book, paper, or document which serves to vouch the truth of accounts, or to confirm and establish facts of any kind; also, any acquittance or receipt showing the payment of a debt; as, the merchant's books are his vouchers for the correctness of his accounts; notes, bonds, receipts, and other writings, are used as vouchers in proving facts. [ 1913 Webster ]

3. (Law) (a) The act of calling in a person to make good his warranty of title in the old form of action for the recovery of lands. (b) The tenant in a writ of right; one who calls in another to establish his warranty of title. In common recoveries, there may be a single voucher or double vouchers. Blackstone. [ 1913 Webster ]

4. A document attesting to a credit against certain defined expenditures; a recipt for prepayment; -- often used in pre-arranged travel plans, to provide evidence of pre-payment of the cost of lodging, transportation, or meals. [ PJC ]