Etymology tree
Proto-Tupi-Guarani *akaju
Old Tupi akaîubor.
Old Tupi akaîubor.
French acajouinflu.
Portuguese acaju
Borrowed from Old Tupi akaîu + French acajou.
The preservation of initial A and the use for the mahogany wood were influenced by French acajou, in comparison to the doublet caju.