Vender has been a published word since at least 1596 according to the full Oxford English Dictionary. You can find it in Francis Bacon's The Elements of the Co

Vender has been a published word since at least 1596 according to the full Oxford English Dictionary. You can find it in Francis Bacon's The Elements of the Common Lawes of England (printed 1630) - https://scholarship.law.wm.edu/oldelawebookes/28/ https://scholarship.law.wm.edu/oldelawebookes/28/ That said, vendor has become more and more the standard spelling in legal texts.