fin
UK[fɪn]US[fɪn]
n
A thin flat part that sticks out from the body of a fish, dolphin, etc., used for swimming and balancing.
n
A part that sticks out from an aircraft, rocket, or car, used for improving its stability or control.
Etymology
The word 'fin' has a direct and ancient lineage. It entered English from the Old English finn, a term shared with other Germanic languages like Middle Dutch vinne. Scholars trace its ultimate origin back to the Proto-Indo-European root pet-, meaning 'to fly' or 'to spread out'. This root is the source of Latin pinna, meaning both 'feather' and 'wing', highlighting the conceptual link between a wing-like appendage used for flight in air and a fin used for movement in water. Over time, the Germanic branch specialized the term for aquatic propulsion, a meaning which was later extended metaphorically to similar stabilizing structures on human-made vehicles.
Analysis
This is a simplex word. It is a loanword from Old English finn, which is of Germanic origin, related to Dutch vin and probably ultimately to Latin pinna 'feather, wing'.
Examples
The shark's dorsal fin cut through the water's surface.
He added a new fin to his surfboard for better maneuverability.
The rocket's guidance fins adjusted its course during ascent.