E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Palm Sunday is so called from the custom of eating figs on that day. The practice arose from the Bible story of Zaccheus, who climbed up into a fig-tree to see Jesus.
Many other festivals have their special foods; as, Michaelmas goose, Christmas, plum-pudding, Shrove Tuesday, pancake day; Ash Wednesday, salt cod; Good Friday, hot cross-buns; pasch-eggs, roast-chestnuts, etc., have their special days.