thingummy
/ˈθɪŋəmɪ/(亦作thingamy)
noun
(pl.-ies)
- informal used to refer to or address a person or thing whose name one has forgotten, does not know, or does not wish to mention〈非正式〉［用以指不知其名, 忘记其名, 不愿称呼其名的人、事物］某某, 那个人; 那东西：
one of those thingummies for keeping all the fire tools together.
那些用于把所有消防工具集拢起来的东西之一。
词源
late 18th cent.: from THING + a meaningless suffix.