Dustman, subs. (common).—1. A personification of sleep: ‘the dustman’s
coming’ = you are getting sleepy. Cf., dust in the eyes.
1821. Pierce Egan, Tom and Jerry, p. 111. A social glass of wine
beguiled an hour or two, till the dustman made his appearance and
gave the hint to Tom and Jerry that it was time to visit their
beds.