'catkin-shaped' is formed from the English noun 'catkin' + the English suffix '-shaped' (meaning 'having the shape of'). 'Catkin' itself was borrowed into English from Dutch 'katteken' (a diminutive of 'kat', meaning 'kitten'), named for a perceived resemblance to a kitten or kitten's tail.

'catkin' entered English in the 17th century from Dutch 'katteken' (lit. 'kitten'); over time 'catkin' came to denote the botanical term for an ament (a slim, drooping flower cluster). The compound 'catkin-shaped' is a modern English formation using '-shaped' to indicate resemblance in form.

Initially the element referred to the resemblance to a 'kitten' (the Dutch root), but in English it evolved to refer specifically to the botanical structure 'catkin'; 'catkin-shaped' now means 'having the form of a catkin'.