American naming has shifted in an unexpected direction over the last two decades: the informal, diminutive, nickname versions of classic names are being given on birth certificates directly. Ellie, Millie, Sadie, Josie, and Charlie for girls; Theo, Archie, and Charlie for boys.
Here's the data.
Girls: Nicknames as given names
Ellie — from #360 to #21
Ellie is the paradigm case. In 2000, Ellie was #360 for girls. In 2024, it's #21 with 6,306 babies.
Ellie was traditionally a nickname for Eleanor, Elizabeth, Eloise, or Ellen. Now it's #21 on its own, while Eleanor is #14 and Elizabeth is #17 — meaning three names that were once the same name are all separately popular. Parents are no longer choosing Eleanor and expecting people to call her Ellie; they're just naming her Ellie.
The appeal is obvious: Ellie is warm, easy to say, easily spelled, friendly without being cutesy, and modern-feeling without being invented. It sounds like a given name in 2024 the way Eliza or Nell would have in 1920.
Millie — from #2,007 to #86
Millie made one of the most dramatic climbs of any name in recent years — from #2,007 in 2000 to #86 in 2024. That's a rise of nearly 2,000 spots in 24 years.
Millie was historically a nickname for Millicent, Mildred, or Amelia. None of those names are primarily responsible for Millie's rise — Amelia is at #3 but has been there since before Millie started climbing. The pull is coming from Millie Bobbie Brown (Stranger Things), who has been one of the most visible young celebrities since 2016 and goes by Millie as her given name (her full name is Millie Bobby Brown).
Sadie — from #243 to #57
Sadie is the oldest story here. Sadie was historically a nickname for Sarah — the original nickname chain was Sarah → Sally → Sadie. In 2024, Sadie is at #57 and Sarah is at #163. The nickname has overtaken the original.
Sadie peaked in the early 1900s and was in gentle decline through most of the 20th century. It's reviving as part of the same vintage wave that's bringing back Hazel, Rosie, and Nellie. Sadie now sounds warm and antique in the most appealing way.
Josie — from #328 to #88
Josie — short for Josephine — is at #88 in 2024, while Josephine itself is at #291. Josie and Josephine have crossed: the informal version is more popular than the formal.
Josie and the Pussycats (comic 1963, film 2001) kept Josie visible through the mid-century decline. Now Josie is exactly the name that fits the current preference for warm, informal, slightly vintage names.
Charlie — from #1,427 to #140 (for girls)
Charlie for girls went from #1,427 in 2000 to #140 in 2024. It's one of the clearest examples of a boys' name (or boys' nickname name) crossing to girls — see gender-shift names.
Charlie for boys went from #450 in 2000 to #176 in 2024. Both versions are climbing simultaneously.
Rosie — from #1,741 to #311
Rosie — diminutive of Rose — went from essentially unused (#1,741 in 2000) to #311 in 2024. The British informal style is the driver here: the UK has used Rosie as a standalone name for decades, and American parents are following the same path. Rose (#115) remains more popular, but Rosie is climbing faster.
Boys: Nicknames as given names
Theo — from #1,289 to #80
Theo is the boys' Ellie: a nickname that has become fully independent. In 2000, Theo was #1,289 for boys — a rare given name, almost always short for Theodore. In 2024, Theo is #80 with 4,110 babies.
Meanwhile, Theodore is #4 with 12,011 babies. Parents are splitting their choices: some choose Theodore and plan to use Theo; others simply name their son Theo. At #80, Theo is too popular to be only a nickname for Theodore (#4) — it's operating independently.
Theo has a different feel than Theodore: quicker, more casual, contemporary. Theodore is the formal option for parents who want flexibility; Theo is for parents who've made the choice already.
Archie — from #2,017 to #333
Archie went from #2,017 in 2000 to #333 in 2024. Prince Harry and Meghan Markle named their son Archie Harrison Mountbatten-Windsor in 2019 — given name Archie, not Archibald. The choice caused discussion (an heir to the British throne using an informal name rather than a formal one), but it reflected and accelerated the informal-name trend. See royal names.
The original Archie (1941 comic strip, now Netflix's Riverdale) has also kept the name continuously visible. Archie is still on its way up.
Ollie — from #3,878 to #1,044
Ollie has climbed but remains far less popular than Oliver (#3). Most parents naming a son Oliver expect the nickname Ollie; fewer are registering Ollie as the given name directly. This may be a genuine preference for the formal option in boys' naming, or simply that parents realize Ollie is shorter than Oliver, which gives them flexibility.
The British influence
The informal-name-as-given-name trend has a clear British origin. In the UK, names like Alfie, Archie, Freddie, Ollie, Theo, Ellie, Millie, and Rosie have been used as formal given names for decades — the British tradition of nickname-names is older and more established than the American one.
Alfie was #1 in England and Wales for years. Archie, Freddie, and Bertie are common British given names even among upper-class families who in previous generations would have used the formal versions. The informal-name trend crossed the Atlantic and American parents have been following it since roughly 2010.
Why this is happening
The formal-to-nickname pressure reversed. For most of the 20th century, formal given names were preferred because they "gave the child options." Naming your daughter Ellie instead of Eleanor was considered limiting. Now that flexibility is less valued — parents are choosing the name they actually want to use rather than the formal version.
Nickname names feel warm and modern simultaneously. Ellie, Millie, Sadie, Josie — these names sound contemporary without sounding invented. They have vintage history (all were common 100 years ago as nicknames) while feeling fresh. They split the difference between the formal vintage revival (Eleanor, Millicent) and purely contemporary names.
Social media and celebrity influence. Millie Bobby Brown as a named celebrity helped Millie. Archie Sussex helped Archie. When a high-profile person uses the informal version as their actual name, it normalizes giving it on a birth certificate.
The middle name shift. More families now use a formal name as the middle name while the informal name is the given name: baby Ellie Charlotte, or Theo James. The formal name is held in reserve for "full name contexts" without restricting the everyday name.
The pattern
The most successful informal names as given names tend to share:
- Two syllables ending in a soft sound (-ee, -ie, -y)
- A clear formal equivalent that's also currently popular (Ellie/Eleanor, Millie/Amelia, Josie/Josephine, Theo/Theodore, Archie/Archibald)
- Vintage American or British use as a standalone name before they became "just nicknames"
The ones struggling to make the transition (Becky, Maggie) tend to feel too specifically mid-century — they haven't crossed to "vintage-charming" yet in the American market.
Explore: Ellie · Millie · Sadie · Josie · Theo · Archie · Charlie
Data: SSA 2000, 2010, 2020, and 2024 US releases. All ranks are within-sex.