item one is looking for; missing article
Refers to a lost or sought-after object. Often used in contexts like searching for a misplaced item or a wanted person/thing.
He has been searching for the missing item for a long time.
This book is the one I was looking for.
Compound of 尋ね (tazune, 'searching') + 物 (mono, 'thing'). The exact historical derivation is straightforward.