Was one of your relatives the Lewda Leake who served in the 10th Mississippi Regiment during the Civil War?
Sorry I couldn't find any info on "Lewda" for you. Perhaps it's a form of "Luther", much as "Lowther" is? Or perhaps it's derived from "Llew", which means "lion" in Welsh.
As for "Leake", my reference source says that this is an English surname for someone who lived by a stream, from the Old Norse word "laeke", meaning "brook". "Leake" is also a placename in Lincolnshire and Nottinghamshire.
An alternate meaning for "Leake" is that it is a name for a grower or seller of leeks, from the Old English word "leac". This would tie in with your Welsh history, as the leek has been a symbol of Wales for centuries, much as the shamrock is a symbol of Ireland.