Meaning

noun large slender food and game fish widely distributed in warm seas (especially around Hawaii)

noun any of various small toothed whales with a beaklike snout; larger than porpoises

originFrom Middle English delphyn, from Latin delphīnus, from Ancient Greek δελφίς (delphís), from δελφύς (delphús, “womb”); the modern form in -ol- is probably influenced by the pronunciation of Middle French dauphin. Compare Swedish delfin. Doublet of dauphin. Displaced native Old English mereswīn (literally “sea pig”), whence English mereswine.

Etymology from Wiktionary, CC BY-SA 3.0