diaphragm: [17] The etymological notion underlying diaphragm is of a sort of ‘fence’ or ‘partition’ within the body. It comes via late Latin diaphragma from Greek diáphragma. This in turn was a derivative of diaphrássein ‘divide off, barricade’, a compound verb formed from the intensive prefix dia- and phrássein ‘fence in, enclose’. Originally in Greek diáphragma was applied to other bodily partitions than that between the thorax and the abdomen – to the septum which divides the two nostrils, for instance. [diaphragm etymology, diaphragm origin, 英语词源]