A cabal is a small group of people united in some close design, usually to promote their private views of or interests in an ideology, state, or other community, often by intrigue and usually unbeknownst to those outside their group. The use of this term usually carries negative connotations of political purpose, conspiracy and secrecy.
The term cabal derives from Cabala (a word that has numerous spelling variations), the Jewish mystical interpretation of the Hebrew scripture. In Hebrew it means "reception" or "tradition", denoting the sod (secret) level of Jewish exegesis. In European culture (Christian Cabala, Hermetic Qabalah) it became associated with occult doctrine or a secret.
It came into English via the French cabale from the medieval Latin cabbala, and was known early in the 17th century through usages linked to Charles I and Oliver Cromwell. By the middle of the 17th century it had developed further to mean some intrigue entered into by a small group and also referred to the group of people so involved, i.e. a semi-secret political clique.
There is a theory that the term took on its present meaning from a group of ministers formed in 1668 ("Cabal ministry") of King Charles II of England (Sir Thomas Clifford, Lord Arlington, the Duke of Buckingham, Lord Ashley, and Lord Lauderdale), whose initial letters coincidentally spelled CABAL, and who were the signatories of the Secret Treaty of Dover that allied England to France in a prospective war against the Netherlands. The theory that the word originated as an acronym from the names of the group of ministers is a folk etymology, although the coincidence was noted at the time and could possibly have popularized its use.