Green’s Dictionary of Slang

anything otherwise unnamed, whether through choice or one’s inability to recall the correct title.

1922		Joyce Ulysses 343: Tossing her hair behind her which had a good enough colour if there had been more of it but with all the thingamerry she was always rubbing into it she couldn’t get it to grow long.
1996		Allsopp Dict. Carib. Eng. Usage.