Căt'kin, n.

noun

n. [Diminutive of cat.] (Bot.) An ament; a species of inflorescence, consisting of many scales ranged along a slender stalk, which is the common receptacle, as in hazel, birch, oak, willow, poplar, &c.; — so called from its resemblance to a cat’s tail.

A botanical drawing of a birch catkin beside a serrated leaf, attached to a short twig.
Catkin of Birch.