Origin of porpoise
- Middle English porpeis from Old French (probably translation of a Germanic compound meaning sea-pig) porc pig (from Latin porcus porko- in Indo-European roots) peis fish (from Latin piscis)
From American Heritage Dictionary of the English Language, 5th Edition
- From Middle English porpeys, purpeys, from Anglo-Norman porpeis, purpeis, Old French pourpois, pourpais, porpeis (“porpoise"), from Vulgar Latin *porcopiscis (“porpoise", literally “pig-fish"), from Latin porcus (“pig") + piscis (“fish"). Compare (in transposed order) obsolete Italian pesce porco and Portuguese peixe porco; also Latin porcus marinus (“sea hog"), akin in formation to German Meerschwein, English mereswine. More at mereswine.