Fionn means "fair" or "white" in Old Irish, referring to light colouring — fair hair, fair skin, or a bright and radiant appearance. It carries connotations of beauty, clarity, and brightness rather than just a physical description.
Fionnuala
fair shoulder
Fisher
Fisherman's son
Fitz
Strong and steadfast
Fitzgerald
Strong castle
Fitzroy
Royal prince
Fjell
Mountain peak
Fletcher
Sword maker or Sword bearer
Fleur
Flower goddess
Flint
Spark of fire
Flor
Petal bloom
Flora
flower, blossoming
Florence
blooming or flourishing
Florent
flourishing, flourishing from
Florian
Floral crown
Florine
Blooming flower
Flossie
Fluffy tuft
Floy
Flower of joy
Floyd
Wanderer or Traveller
Flynn
son of Finn, red-haired
Ford
strong and sturdy
Forest
related to a forest or woods
Forrest
dweller by the forest
Fortune
good luck, prosperous
Foster
Child caregiver
Fox
Cunning or clever, possibly derived from Old English word 'fox'