The word 'yellowfin' is a transparent Modern English compound, formed by directly combining two native Germanic elements. 'Yellow' descends from the Proto-Germanic gelwaz, which itself derives from the Proto-Indo-European root ghel-, meaning 'to shine' and associated with bright colors like yellow and green. 'Fin' originates from Proto-Germanic fenno, likely connected to the idea of a projecting flap or feather. The compound's logic is purely descriptive, naming the marine creature by its most visually prominent anatomical feature—its brightly colored fins. This straightforward naming convention is common in English for fish species, such as 'bluefin' or 'blackfin'.

Structure: yellow (color) + fin (body part) - yellow: From Old English geolu, geolwe, of Germanic origin; related to German gelb. Functions as an adjective/color descriptor. - fin: From Old English finn, of Germanic origin; related to Dutch vin and probably to Latin pinna 'feather, wing'. Functions as a noun denoting a projecting part.