A proffer is an offer made prior to any formal negotiations.
In a trial, to proffer (sometimes profer) is to offer evidence in support of an argument (for example, as used in U.S. law[1]), or elements of an affirmative defense or offense.
For example, in support of a particular argument, a party may proffer documentary evidence or witnesses.
As in business, a proffer can be a sign of "good faith" a first offer or proposal, to show a willingness to "barter".
The word proffer is derived from Anglo-French "por-", forth, and "offrir", to offer.