thingamajig
n.a word you use when you can't remember or don't know the name of a small object. It fills the gap when "thing" feels too vague.
n.a placeholder noun for a small object whose name is unknown, forgotten, or deemed unimportant. Informal and colloquial.
“Pass me that thingamajig on the table.”
“He rummaged through his toolbox until he found the little thingamajig that tightens the pipe fittings.”
“The inventor's workshop was cluttered with half-finished prototypes, springs, and nameless thingamajigs that only he could identify.”
From thingum (or thingummy) + jig, patterned metrically after gobbledygook and rigamarole; compare thingamabob and similar formations. Earliest attestation 1824, as thingumajigs.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.