It provides the immediate root (Latin, Greek, Arabic, etc.) and often the chain of transition through other languages like French or Italian.
That said, the most famous and authoritative etymological dictionary for Spanish is (later expanded by José Antonio Pascual). The RAE often relies on Corominas’s work. diccionario etimologico rae
For a deeper, more academic look at how words have changed over time, the RAE is developing the Diccionario Histórico de la Lengua Española (DHLE) . It provides the immediate root (Latin, Greek, Arabic, etc
If you need to write a paper on this topic, here is a structured outline and key points you can use. For a deeper, more academic look at how
If you meant a (e.g., the RAE’s Nuevo tesoro lexicográfico de la lengua española or a specific 19th-century etymological dictionary published under RAE auspices), let me know and I can refine the response. Otherwise, the above gives you a clear academic paper framework on the subject.