3 ideas
Imagining an addressee with no prior experience of the world strips away the shared assumptions that let you skip over an object. You are forced to state what the thing literally is, what it does, and why it exists. That naive, complete description exposes how odd and contingent the familiar actually is.
The more often we encounter something, the more perception shrinks to recognition. We register the category and stop seeing the thing itself. Habit protects us from being overwhelmed, but it also erases the strangeness and wonder of ordinary existence, and only deliberate attention can recover them.
Describing a body part or everyday object in plain physical terms, rather than by its familiar name and function, renders it alien. The strangeness was always present; the name had simply covered it over.