You may speak of them as Mr. What's-his-name, or Miss thingummy, but you must give them tea or coffee or cake or sandwiches, or whatever is brought in on a tray.
"Somehow Good"
William de Morgan
Because if we hadn't, the Bottle Man would never have come sailing down to see us, and he might still be thinking Aunt Ailsa had married the Mr. thingummy, when she hadn't at all.
"Us and the Bottleman"
Edith Ballinger Price
"This," said Plummer sombrely, gazing over the rail into the darkness, "is the place where that fellow what's-his-name jumped off in the reign of thingummy, isn't it?"
"A Damsel in Distress"
Pelham Grenville Wodehouse