Heading that Lovecraft letter, the huge letter to Woodburn Harris (“WARNING! Don’t try to read this all at once”), Lovecraft uses for his letterhead…

Valentine Boiling Fitz-Randolph Byrd, of Virginia
10 Barnes Street
November 9, 1929

Why does he assume the first name “Valentine”?

Well, firstly because he could. Valentine could be a real name of the period in the English-speaking world. For instance, a Canadian-born colleague of Tolkien’s was named Eric Valentine Gordon (‘E.V. Gordon’). And an Edwin Valentine Mitchell edited The Pleasures of Walking (1948). The name was not uncommon.

It was more common in the U.S. state of Virginia. In a letter of 1936 Lovecraft suggests “Henry S. Valentine” as an ideal name for a fictional man from Richmond, Virginia. Thus the “of Virginia” bit of his 1929 letterhead. Lovecraft had been in Richmond, and had probably encountered a number of men by that name.

Lovecraft the Roman was also familiar with Emperor Valentinian, the last great western Emperor of Ancient Rome.

He would also have know that the Valentine Museum was one of the best known Poe museums of the period. Lovecraft also knew of the then-venerable sculptor Edward Valentine, who he envied because as a boy Valentine had known Poe.

He may have had a more personal fondness for the name because it occurred in his family tree. His aunt Annie E. (Phillips) Gamwell had several cousins of that name. Also in the family tree was a Rev. Valentine Rathbone b. 1724. This vicar was in the line that distantly connected him with Barlow’s family tree. The connection is discussed in a letter to Barlow of 22nd May 1936. The printed Barlow letters (O Fortunate Floridian) appear to omit a note enclosed with the letter, which read: “P.S. I burst this letter open again for nothing! My aunt recalled hearing of a Valentine Rathbone”.

As for the other names… “Boiling” is certainly not a common first or middle name, though it may perhaps be a self-depreciating allusion to ‘pot-boiler’ stories. “Fitz-Randolph” evokes the high British aristocracy, but also his own Randolph Carter fictional alter-ego. While “Byrd” was the name of the famous Antarctic explorer of the era.