Even Greener Pastures

Almost. It's individual language usage.
Say your daughter used to call a pacifier "a lala". You remember this when going to the shop to buy one for your grandchild, and accidentally ask the shop assistant for a "lala". Then, when they look at you strangely, you can say "Sorry, idiolectal use!" 

It'll come in handy once I'm going gaga with age, I'm sure. Provided I can still remember it by then.