languor
definition
a state of tiredness or lethargy often associated with a relaxed or dreamy feeling
example
After a long afternoon under the sun, she succumbed to a delightful languor, drifting off into a peaceful nap.
synonyms
fatiguelethargylanguidness
word origin — From Latin 'languor', meaning 'faintness, weakness', from 'languere', meaning 'to be weak or faint'.