Coconut

Shaking palm trees along an ocean beach is the only source, and it is worth doing on the way past rather than as a trip of its own. The buff is the bottom food tier, so eating one raw is a stopgap and not what you want going into a boss.

The real value now is Shimmer. Drop one in and it becomes Ambrosia, which is a far better meal, so a stack of coconuts converts into a stack of top-tier food once you have Shimmer access. Save them for that. Corrupt, crimson and hallowed palms all shake out the same fruit, so a converted beach still works fine. The tooltip is a Monty Python and the Holy Grail line.