I’m referring to a suffix of English names. Where did *-thwaite * come from and what did it originally mean? I refer to comedian Bob Goldthwaite, actor Robert Cornthwaite, politician Yvonne Braithwaite Burke (I now live in her supervisorial district in Los Angeles County, and have in fact voted for her.)
As someone who speaks (well reads anyway) a Celtic language, I would assume that -waite and -waithe means water and work respectively. The “th” that you have in front of it would be a mutation from a “d” or “t” most likely. Anyway, I think Bobcat Goldwaithe doesn’t have the “th” in his name. It makes more sense that way. Many of the suffixes from the Celtic branch languages drifted into English due to the natives proximity to what is now England. Following this logic Goldwaithe means gold worker (or more accurately gold smith, ie one who works with gold), Cornthwaite means Cornish Water (I assume this persons ancestors were fisherman off of Cornwall), and Braithwaite means grey (or muddy) water (yet another way of being called a fisherman). -waite I believe is old English for water wheras -waithe is a Welsh derrivative of “to work”.
I hope this answered your question.
SC
I hope so, too, SC. Thanks. 
thwaite: “A piece of ground; especially a piece of ground cleared from forest or reclaimed from waste. . . hence, the surname Thwaites”
–OED
No, I’ve always thought it was not of Celtic origin, but rather Norse, hence its popularity in, for instance, Yorkshire. Sadly, I have no OED, but what Collins English Dictionary has to say is: