…inor noble from Shropshire who was not yet twenty, the child would go onto be called Henry Fitzroy. The name Fitz came from the French fils, which meant ‘son of’. It’s unclear why he was given the name Fitzroy over say Fitzwilliam, but ultimately it didn’t matter.
Fitz = 'son of', and roy= 'king' (from Old French 'Roy', Modern French 'Roi')
'Fitzroy' = 'Son of the King'
He might equally have been called 'Fitzhenry'.