*keu

The core idea of this root was:

observing, watching, perceiving

It’s the origin of hören and to hear (which is acoustically perceiving, observing) and also of German schauen, which is about looking at.
The English brother of schauen, to show, shifted from mere seeing toward showing – first, showing what you’re seeing and then showing in the more general sense.

It’s also the origin of  German schön, which was originally “something you like to watch” and of the English caution which comes from Latin and was about watching in a sense of being on guard.

Some English relatives:

• to show (showing what you see)
• to hear (perceiving acoustically)
• caution (observing danger)
• sheen (similar to German schön)