Knack, n. 1. A petty contrivance; a toy; a plaything; a knickknack.
A knack, a toy, a trick, a baby's cap. Shak.
2. A readiness in performance; aptness at doing something; skill; facility; dexterity.
The fellow... has not the knack with his shears. B. Jonson.
The dean was famous in his time,
And had a kind of knack at rhyme. Swift.
3. Something performed, or to be done, requiring aptness and dexterity; a trick; a device. “The knacks of japers.” Chaucer.
For how should equal colors do the knack! Pope.