The man was Charles Cunningham Boycott, a retired captain from the British army that worked as a land agent for a man named Lord Erne. In 1880, the community he oversaw had a campaign called the Three Fs, which called for Fair Rent, Fixity of Tenure and Free Sale of land.
The community began a campaign of isolation against Boycott in the local community. This included not allowing him in stores, refusing his laundry service, and even threatening the kid who delivered his mail.
The campaign against him became a well-covered cause in the British press. They supported Boycott and saw it as a victimization of a servant by Irish nationalists. The people behind the campaign had trouble deciding what to call what they were doing to him, in order to explain it to less educated people.
The correct term was that he was being 'socially excommunicated,' 'ostracized,' but people felt that term was too complicated to explain to uneducated people. So instead, they turned his name into a verb! Captain Boycott. Sounds almost like a meme doesn't it?