Webster's Revised Unabridged Dictionary · 1913

Knack

Knack (nak) , intransitive verb

[Probably of imitative origin; compare German knacken to break, Danish knage to crack, and English knock.]

1.
To crack; to make a sharp, abrupt noise to chink. [Obsolete or Provincial English] — Bp. Hall
2.
To speak affectedly. [Provincial English] — Halliwell

Knack , noun

1.
A petty contrivance; a toy; a plaything; a knickknack.
A knack, a toy, a trick, a baby's cap. — Shakespeare
2.
A readiness in performance; aptness at doing a specific task; skill; aptitude; facility; dexterity; -- often used with for; as, a knack for playing the guitar.
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