What does the root word bell-us mean?

The root word "bell-" is not a recognized root word in English. It's likely you're thinking of "bell" which is a standalone word with its own meaning and origin.

Bell comes from the Old English word "belle", which itself is derived from the Proto-Germanic word "balla". This word referred to a hollow, resonant object often used for signaling or making a sound.

While "bell" doesn't have a specific root word in the way many English words do, its meaning is associated with the sound and shape of bells, which have been used for various purposes throughout history.