It seems like people named Elvis fall into three categories:
Elvis Presley
People named after Elvis Presley
People who use Elvis Costello as a professional pseudoynm but who were born Declan MacManus
Who in the world is or was named Elvis before The King became famous? Is the name that unique? Of what ethnicity does it come? Is it just the most likely name that would be thought of by a couple named Vernon and Gladys?
Many of those results are to Croatian people named “Elvis”, so I’m going to conclude that either:
Elvis began (ethnically) as a Croatian name, that the (non-slavic) Presleys chose to name their child; or,
Croatians and Croatian-Americans are largely Elvis fans, and rabidly so to the point that many were named Elvis in anticipation of the Rock-n-Roll Sensation Himself.
In my mother’s family there are a couple occurences of “Alvis”/“Alvus” which is pretty close. All very pre-The King. On my wife’s side there’s an “Elva” which is one of the female forms of the name. But we’re talking pre-1930s. Nothing similar in recent decades. A lot of common names from a couple generations ago are frowned upon. My wife has “Sophronia” and “Euphramia” (twice and in different branches!) in her genealogy.
Our friend the Social Security Death Index shows that in 1935, the year Elvis Presley saw the light of day in Tupelo, Mississippi, there were at least 12 other men named Elvis born that year. (The SSDI includes only deceased persons.)
In 1955, the last year of Elvis Presley’s relative anonymity, there were at least 3 men born with the name Elvis.
Going back to 1900, where we can get a better estimate of the actual number of Elvises born that year, the SSDI has 55 men by that name. The states in which their Social Security numbers were issued (in 1936 or later):