The naming of stars by assigning them to constellations and giving Greek letters is attributed to ancient Greek astronomers, primarily Claudius Ptolemy, who lived in the 2nd century AD.

Here's a breakdown:

* Constellations: Ancient civilizations across the globe, including the Greeks, Babylonians, Egyptians, and Chinese, developed their own systems for grouping stars into constellations. These constellations were often based on mythological figures, animals, or objects.

* Greek Letters: Ptolemy's work, "Almagest," cataloged the positions and brightness of around 1,000 stars. He organized them into the constellations already established and assigned them Greek letters (alpha, beta, gamma, etc.) in order of decreasing brightness within each constellation. This system is still used today.

It's important to note that the practice of naming stars has a long history, dating back even further than Ptolemy. However, his work was so influential that it became the standard for assigning Greek letters to stars.

While Ptolemy's system is still used, it has been expanded and modified over the centuries. For example, modern astronomers now use a much more comprehensive system, including names for fainter stars and stars outside of the original 1,000.