derivation

The source of a word or expression. English words are derived from a variety of other languages (see borrowing), especially Greek (for example, hexagon from hex and -gonos meaning ‘six-angled’), Latin (for example, mission from mittere meaning ‘to send’), Anglo-Saxon (for example, blood from blod), and, after the Norman Conquest, French (for example, entreat from entraiter).

Many current expressions have survived the practices that gave rise to them; they are dead metaphors. ‘Getting the sack’, for instance, is derived from the time when workers brought their own tools in a sack. ‘Get your sack’ meant you had lost your job.