One common name for this anti-pattern is Mystery Meat. As described in Designing Web Interfaces:
Have you ever found a can in the back of the pantry whose label has
long since fallen off? The only way to identify this mystery meat is
to open it. Unidentifiable icons are pretty much the same as a row of
unlabeled cans. You have to hover over each icon and hope for a tool
tip to label it. Even worse is when no tool tip is available. The
easiest way to avoid this predicament is to use either a text label or
combine an icon with a text label. Mystery Meat is a common
anti-pattern that occurs when you have to hover over an item to
understand how to use it.
This is the Wikipedia article that you're thinking of (with the Moon example):
Mystery meat navigation (also known as MMN) is a disparaging term
coined in 1998 by Vincent Flanders, author and designer of the website
Web Pages That Suck, to describe a web page where the destination of
the link is not visible until the user points their cursor at it.
Such interfaces lack a user-centered design, emphasizing aesthetic
appearance, white space, and the concealment of relevant information
over basic practicality and functionality.