A fantastic example of my favorite kind of Wikipedia entry: placeholder name.
Placeholder names are words that can refer to objects or people whose names are either irrelevant or unknown in the context in which it is being discussed.
Whatchamacallit, junk, widget, gizmo, Joe Blow, shitload, Podunk, and beer o'clock are all examples. Placeholder names are also used extensively in non-English languages.
The German equivalent to the English John Doe for males and Jane Doe for females would be Max Mustermann and Erika Mustermann, respectively. For many years, Erika Mustermann was used on the sample picture of German id-cards ("Personalausweis"). In Austria, Max Mustermann is used instead. Sometimes the term Musterfrau is used as the last name placeholder, possibly because it is felt to be more politically correct genderwise.
(via gulfstream)