A more thorough explanation:

Ebba et Fluctus is a Latin term that means "ebb and flow". It refers to the rise and fall of the tide in the ocean. This term was used in ancient times to describe the regular movement of the ocean's water.

For example, when the tide is low, the water recedes from the shore, and this is called the ebb. When the tide is high, the water comes back in, and this is called the flow. This movement of the water is constant and predictable, and it is caused by the gravitational pull of the moon and the sun.

In the past, people used the term ebba et fluctus to measure time. They would count the time it took for one ebb and flow of the tide, which was about 12 hours and 25 minutes. This was an important measurement for sailors and fishermen, who needed to know when the tide would be high or low in order to navigate their boats safely.