Another revelation to me in the Feurth sefer was the way that a name change for a seriously ill person, ל”ע, was performed there in those days (approximately three hundred years ago).
In volume one, on page 342, the process is described as follows –
The ארון קודש is opened and a מי שברך (more elaborate version than the standard mi shebeirach for cholim) using the current name of the חולה is recited twice, asking for a רפואה in merit of צדקה given. Then, a גורל is cast in the following manner. A תנ”ך would be opened at random by a youngster under supervision of the שמש. If, for example, the choleh was male, the first male name on the page where it was opened, would be taken as the new name for the choleh. In the case he discusses, the name עלי came up by this method, and was added (not a common name among אשכנזים). And then a third mi shebeirach, as above, would be said, using the new name of the choleh.
Nowadays, from the little I know about this, it is not done in such a ‘random’ manner, and usually only certain names which imply health and good fortune for the choleh, such as חיים, are chosen. See the sefer for more details.
Update: The piece on this in the ספר מנהגים of Feurth from close to two hundred fifty years ago, clearly showing the classical manner of it, can be viewed starting at the bottom of this page, and continuing for the next two pages (pages 57-59 in the Hebrewbooks.org file).
TREASURES OF ASHKENAZ 