Here’s a concise review of the RAE Diccionario Etimológico (the etymological dictionary of the Real Academia Española), keeping in mind that the RAE’s main etymological reference is actually the Diccionario de la lengua española (DLE) with etymologies, plus the Nuevo diccionario histórico (NDH) in progress.
Use the RAE’s free online dictionary for a fast, trustworthy root. If you need detailed historical context, borrow Corominas or the Nuevo diccionario histórico (when available). The RAE is reliable but minimal — a good starting point, not a final destination. rae diccionario etimologico
★★★☆☆ (3/5 for dedicated etymology needs) Here’s a concise review of the RAE Diccionario