Placeholder names are words that can refer to objects or people whose names are either temporarily forgotten, irrelevant, or unknown in the context in which they are being discussed. "Whatchamacallit" (for objects) and "Whatshisname" or "Whatshername" (for men and women, respectively) are defining examples.
Linguistic role
These placeholders typically function grammatically as nouns and can be used for people (e.g., John Doe, Jane Doe), objects (e.g., widget) or places (e.g., Timbuktu). They share a property with pronouns, because their referents must be supplied by context; but, ...