Tracing back my surname (specific to MY genealogy, mind you!) suggests the following sequence of spelling changes: Sperlingham-->Sperlingh-->Sperling-->Sparling-->Sparlin.
I probably had an ancestor, Jan or Pieter or Niels, etc., who lived in the town of Sperlingham, thus, Jan of Sperlingham. I give this ancestor a Dutch first name, because his descendants later settled in New Amsterdam, and their names are found on the rolls of the Dutch Reformed Churches.
Sperling might refer to a fish--might! I've tried to track down the etymology, but it is ambiguous. If it does refer to a fish, I like to imagine that Sperlingham was along a coastline, perhaps a fishing village and that the great number of men were fisherman.
When Jan & family traveled to America, the name, "Jan of the town of Sperlingh," was shortened to Jan Sperlingh and so on. Some of the changes were, undoubtedly, errors, but might also have been personal preference. In one family, at least, from Indiana, the sons variously spelled their name either with or without the terminal "g," giving rise to Sparlins and Sparlings who were first cousins.
I am the descendant of one of these brothers who dropped the "g," and now with Social Security numbers firmly rooted in our society, there's less chance the spelling will change soon. However, a SSN, as immutable as that seems to us, is only a blip in history, and I have no doubt that hundreds of years from now, a descendant with a similar--but not exact--name will be squinting at my name, Kecia Sparlin, and making up stories about me, too.