Most Well-Known Person named . . .

Sarah.

In order, IMHO:

Sarah Palin.

Sarah Michelle Gellar.

Sarah Silverman.

Sarah Bernhardt (actually the first one I thought of, but she died in 1923, so few who saw her perform on the stage are still around to tell the tale)

Ellen

Ellen Degeneres

Ellen Page

Ellen Pompeo

Nancy.

Sara (Noznisky-Novoletsky-Lownds-Dylan), the “Sad Eyed Lady of the Lowlands.” here of her hereor here

Nancy Kerrigan

Nancy Reagan

comic strip Nancy, the niece of Fritzi Ritz and girlfiend of Sluggo

and: Nicholas

Nicholas Cage

Saint Nicholas

Nathan Lane

Sarah Plain and Tall

Next: Wilfred

I was going to say actor Wilfred Hyde-WHite, but I looked it up and he’s actually a Wilfrid.

So, for me, it’s a tie between poet Wilfred Owen and boxer Wilfred Benitez.

Of course, if fictional characters count, Wilfred of Ivanhoe is far more famous than any of them.

New name: Jeremiah

Spelling variations count, according to the OP.

The prophet Jeremiah

Jeremiah Johnson

Jeremiah Bullfrog.

New name: Chuck

Chuck Berry
Or Chuck Hagel
Or Chucky (fictional murderous doll)

Damn, hard to choose just one.

ETA Chuck Norris!

Chuck Bartowski (from TV show Chuck)

“Two Buck Chuck,” the nickname for Trader Joe’s Charles Shaw wine, that used to retail for $2 (and may still, for all I know).

No, not as well known as Chuck Berry, Chuck Norris, or Chucky. But still wanted to sneak it in there.

Bartholemew.

Bartholomew, one of the Apostles.

Manny.

Okay, let’s use the Wikipedia standard. When you start typing a query into Wikipedia, it tries to guess what you’re going to ask for based on the most common queries that started like yours did.

The first names Wikipedia guessed:

Erica Pereira
Blair Underwood
Constance Bennett
Eloise Hawking
Nathaniel Hawthorne
Sarah Palin
Ellen Degeneres
Nancy Pelosi
Nicholas II of Russia
Wilfred Owen
Jeremiah Wright
Chuck Berry
Bartholemew Simpson
Manny Pacquiao