The plant
editWe have: "any plant of the genus Rhinanthus, whose seeds produce a rattling noise in the wind". Chambers 1908 has: "an annual meadow herb: a lousewort". But lousewort is apparently Pedicularis...? Equinox ◑ 14:12, 16 November 2019 (UTC)
Green's Newspeak (1984) says that a policeman "on the rattle" is one who been reported to a superior and faces punishment. The only use I could find in Google Books was The Spectator vol 178, page 619 (from the year 1947), and I can't access the text in readable form, beyond "he may find himself 'on the rattle' - placed on a report". Equinox ◑ 20:02, 12 January 2021 (UTC)