(To ). To boycott a person is to refuse to deal with him, to take any notice of him, or even to sell to him. The term arose in 1881, when Captain Boycott, an Irish landlord, was thus ostracised by the Irish agrarian insurgents. The custom of ostracising is of very old standing. St. Paul exhorts Christians to “boycott” idolaters (2 Cor. vi. 17); and the Jews “boycotted” the Samaritans. The French phrases, Damner une boutique and Damner une ville, convey the same idea; and the Catholic Church anathematises and interdicts freely.
“One word as to the way in which a man should be boycotted. When any man has taken a farm from which a tenant has been evicted, or is a grabber, let everyone in the parish turn his back on him; have no communication with him, have no dealings with him. You need never say an unkind word to him; but never say anything at all to him. If you must meet him in fair, walk away from him silently. Do him no violence, but have no dealings with him. Let every man's door be closed against him; and make him feel himself a stranger and a castaway in his own neighbourhood.” —J. Dillon, M.P. (Speech to the Land League, Fch. 26, 1881).
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894