Why is the ninth month called September?
1540s, "secret storehouse, treasure chamber," from Middle French cabinet "small room" (16c.), diminutive of Old French cabane "cabin" (see cabin); perhaps influenced by (or rather, from) Italian gabbinetto, diminutive of gabbia, from Latin cavea "stall, stoop, cage, den for animals" (see cave (n.)).
Meaning "case for safe-keeping" (of papers, liquor, etc.) is from 1540s, gradually shading to mean a piece of furniture that does this. Sense of "private room where advisors meet" (c.1600) led to modern political meaning (1640s); perhaps originally short for cabinet council (1630s); cf. board (n.1) in its evolution from place where some group meets to the word for the group that meets there.
A select group of officials who advise the head of government. In nations governed by parliaments, such as Britain, the members of the cabinet typically have seats in parliament. (Compare cabinet under “American Politics.”)
A group of presidential advisers, composed of the heads of the fourteen government departments (the secretaries of the Department of Agriculture, Department of Commerce, Department of Defense, Department of Education, Department of Energy, Department of Health and Human Services, Department of Housing and Urban Development, Department of the Interior, Department of Labor, Department of State, Department of Transportation, Department of the Treasury, Department of Veterans Affairs, and the attorney general (head of the Department of Justice) — all of whom are appointed by the president and confirmed by the Senate) and a few other select government officials. Theoretically, the cabinet is charged with debating major policy issues and recommending action by the executive branch; the actual influence of the cabinet, however, is limited by competition from other advisory staffs.