odd piece; incomplete set; odds and ends
Refers to leftover, mismatched, or incomplete items, often from a set or collection. Can be used for physical objects or abstractly for something that doesn't fit in.
This plate is an odd piece, left over from a set.
The drawer is full of odds and ends.
Compound of 半端 (はんぱ, 'incomplete, fragmentary') + 物 (もの, 'thing'). The exact historical derivation is uncertain, but the meaning is transparent from its components.