The blackball was used in elections to membership of a Gentlemen's club (and similarly organised institutions, such as Freemasonry). The principle of such a club was that it was self-perpetuating: i.e. new members could only be elected by existing members. This was to ensure that new members were congenial to the old members, which helped to preserve the ethos (and exclusivity) of the club. The term is also used as a synonym to blacklist. A Gentlemens club is a members club, originally for male members of the English gentry. ... the Square and Compasses Freemasonry is a worldwide fraternal organization. ... Synonyms (in ancient Greek syn συν = plus and onoma όνομα = name) are different words with similar or identical meanings. ... A blacklist is a list or register of people who, for one reason or another, are being denied a particular privilege, service, or mobility. ...

The favoured method of election was by the ballot box which was a wooden box into which those participating in the election placed a small ball or ballot. A white ball signified support; a black ball signified opposition. The box was usually designed so that observers could not see how the voter was voting - it was all done under cover of the box, or of a combination of a cloth and the box itself, this being the origin of the secret ballot.

Different voting systems applied from club to club and from time to time: thus, in some cases even a single black ball would be fatal to the candidate's election, whilst, in larger clubs, rules were put in place to ensure that a single person could not exercise a right of veto to the detriment of the future of the club.

The following example from the rules of election to the Travellers Club, which is quoted from Dickens's Dictionary of London (published in 1879), provides an illustration of the principle:- Overview The Travellers Club is a gentlemens club standing at 106 Pall Mall, London. ...

"The members elect by ballot. When 12 and under 18 members ballot, one black ball, if repeated, shall exclude; if 18 and upwards ballot, two black balls exclude, and the ballot cannot be repeated. The presence of 12 members is necessary for a ballot."

The origins of the blackball lie in ancient Greece, where people were excluded by use of the ostrakhon (shell or potsherd) as a ballot in voting: see ostracize. In modern parlance, to ostracize means to exclude someone from society or from a community, by not communicating with or even noticing them, similar to shunning. ...