The name has many variations and a few derivations, mainly as a result of the difficulty in representing the initial double-L for non-Welsh speakers and the translation of the Welsh diphthong wy.
[1] The name Lloyd/Llwyd originates with the Welsh adjective llwyd, usually understood to mean 'grey' and which can be distinguished as a "fixed epithet" passed on from one generation to the next, as early as the 14th century.
[1] T. J. and Prys Morgan note: ... in general it is likely the adjective llwyd referred to some sort of brown hair when associated with a personal name.
HBr 495 is wrong in stating "the third son was called David Llwyd, I presume, from his grey hair in early life".
failing to realize that llwyd is one of the exceptions.Variations most often encountered illustrate the degree to which Anglo-Norman and later English scribes sought to render the sounds unfamiliar to their own diction.
[1] Variations include: Floyd, Flewett, Flewitt, Flood, Floed, Floyde, Flowitt, Flude, Fludd, Fludde, Flude, Fluett, Fluat, Flyd, Flyde, Lide, Lhuyd, Loud, Loulld, Luyd, Llowyde, Llowyd, Lloyed, Lloilld, Llwyed, Thoyd, Thloyd, and Thllewyd.