What term describes the type of analysis of artworks that involves interpreting symbols, themes, and subject matter as sources of meaning—such as that conducted by the influential art historian erwin panofsky?

The right answer is iconography.

Explanation: Just to elaborate a little on the answer, it can be added that German art historian Erwin Panofsky (1892-1968) devised a method to analyse works of art—specifically from the Renaissance—at various levels of understanding. The primary level focuses on the formal features or properties of the work and is called the pre-iconographical description. The second level analyzes the theme and the subject matter, which requires a more specific art-historical knowledge—most people can identify a female figure in a painting, but it requires knowledge to identify her as the Virgin Mary. Finally, the third level studies the symbolism of the work. In other words, it attempts at understanding the work, and the function that it fulfilled, in its original context. This is known as the iconological analysis.