When I got married, one of the questions on the license was mother's maiden name. I knew I was going to have to spell it, after all, I wasn't getting married in the small town where I grew up.
I had to spell it three times before he understood--and it was only five letters--Ufkes.
Chances are your ancestor was not asked to spell the information he provided on a record. And if you think he did spell it to the clerk, how can you really be certain? After all, you weren't there when the clerk ask great-great-grandfather for the information on his marriage.
And if you were there---there were a lot of questions that I bet you wish you asked ;-)