The historicity of Robin Hood has been debated for centuries. but Robert was a very common given name in medieval England, and 'Robin' (or Robyn) was its very common diminutive, especially in the 13th century. The surname Hood (or Hude, Hode, etc.) was also fairly common because it referred either to a hooder, who was a maker of hoods, or alternatively to somebody who wore a hood as a head-covering. It is therefore not surprising that medieval records mention a number of people called 'Robert Hood' or 'Robin Hood', some of whom are known to have fallen foul of the law.
Another view on the origin of the name is that 'hood' was a common dialectical form of 'wood'; and that the outlaw's name has been given as 'Robin Wood'.