Before reading Drury’s splendid biography of the poet George Herbert, I knew ‘imp’ only as a small being of occasional mischievousness.
But it is also a falconry term, which the OED defines as: ‘to engraft feathers in a damaged wing to restore or improve its power of flight’. Herbert uses it in this sense as a metaphor in his ‘Easter Wings’ (a poem which in form also echoes the spread of wings), grafting his own weaker wing on to that of Christ:
Let me combine,
And feel thy victory:
For if I imp my wing on thine,
Affliction shall advance the flight in me.’
Source: George Herbert, ‘Easter Wings’, quoted in John Drury, Music at Midnight: The Life and Poetry of George Herbert (London: Penguin Books, 2014), p. 275