languor

Concise Oxford English Dictionary © 2008 Oxford University Press:
languor /ˈlaŋgə/

▶noun

• 1 tiredness or inactivity, especially when pleasurable.

• 2 an oppressive stillness of the air.

– derivatives
languorous adjective,
languorously adverb.

– origin ME (orig. in the sense ‘illness, distress’, later ‘faintness, lassitude’): via OFr. from L., from languere (see languish).