What is the name of the reveal-menu-bar-on-Alt interaction?

Firefox has the following interaction on the GNOME desktop (observed in Firefox ~55, GNOME ~3.26):

• Starts with menu bar hidden
• When you click Alt the menu bar appears [1] (and stays visible after the key is released)
• When you press Alt again, the menu bar is hidden

Does this interaction have a name?

[1]: For example, when starting the Alt + F combo to open the "File" menu.