Not knitwear but an umbrella term for expressions we use when we can't remember the word for something or can't be bothered to think what is; words such as
Thingamabob
Oojamaflip
Whatchamacallit
Thingamajig
Modern English has a very rich collection of words like this, with new ones being coined as recently as the second half the 20th century. I think the official name for this category of words is undifferentiated placeholders, rather a mouthful, and although it's not made it into the Oxford English Dictionary yet, the word kadigan seems to be an alternative popular amongst people interested in this kind of thing.
The origins of kadigan are debated. One suggestion is that it was coined by the American word lover Willard R. Espy around 1960 but the Useless Etymology websote suggest some other possibilities.