calm: [14] The underlying meaning of calm seems to be not far removed from ‘siesta’. It comes ultimately from Greek kauma ‘heat’, which was borrowed into late Latin as cauma. This appears to have been applied progressively to the ‘great heat of the midday sun’, to ‘rest taken during this period’, and finally to simply ‘quietness, absence of activity’. Cauma passed into Old Italian as calma, and English seems to have got the word from Italian. [calm etymology, calm origin, 英语词源]