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Si

UnisexBoys' nameGirls' name

Diminutive of Simon or Simone or Silas

Si has been given to 185 babies in the U.S. since 1927. It was used fewer than 5 times in 2025, so it doesn't appear in the latest year's list — today it's a genuinely uncommon pick. Its peak year was 2013, with 15 recorded. It's used for both sexes: 90% boys, 10% girls all-time.

Babies named Si, 2017

1 in 596,000

Si over time, 1880–2025

BoysGirls
05101518801900192019401960198020002020

Based on births in the U.S. Babies given the name each year. Hover the chart — or focus it and use the arrow keys — for any year. Gaps mean the name was given fewer than 5 times that year; these counts are unpublished.

Girls or boys — Si over time

In 2017, Si went to 0% girls and 100% boys.

19272017

A sex is only published in years it reached five applications, so a stretch at 0% or 100% means the other side stayed under that floor — not that it was never used.

Si: meaning, origin, and history

Diminutive of Simon or Simone or Silas

Deeper origin not confirmed in the cited records

What Si means

Si is a diminutive of Simon or Simone or Silas.

Dictionary etymologyReferences, data & attribution

From clipping of various words beginning with the syllable /saɪ/.

Excerpt from Wiktionary: Si (English) · CC BY-SA 4.0

Wiktionary material is available under CC BY-SA 4.0.

Origin, language, and formation

Si is used in English.

Related names and everyday forms

Related names include Simon, Simone and Silas.

Pronunciation and spelling

In English, Si is pronounced /saɪ/.

American usage and historical context

In the United States, 166 boys were recorded with the name Si between 1927 and 2017. Its highest annual count was 15 in 2013; its best national rank was #2,931 in 1934.

In the United States, 19 girls were recorded with the name Si between 2006 and 2011. Its highest annual count was 8 in 2011; its best national rank was #13,180 in 2011.

How common is Si?

Si had fewer than 5 recorded uses in 2025, so these figures use 2017, the last year it was published.

Among all babies, 2017
1 in 596,000
6 of 3,577,106 births
Among boys only
1 in 308,000
<0.01% of boys
Rank, 2017
Unranked
Fewer than 5 uses
Coin-flip room size
413,245 kids
Even odds of a second one

Where Si sits on the popularity scale

Rarest published (5 a year)#1 — Liam (20,818)

Chance at least one other child shares the name

If the other children were drawn at random from the 2017 national name distribution. Real classrooms cluster by region and community, so treat these as a floor, not a ceiling.

Class of 20Under 1%
Class of 30Under 1%
Grade of 100Under 1%
School of 500Under 1%

Put another way: gather 413,245 children born in 2017 and it's an even bet that one of them is another Si. In a class of 30 the chance is Under 1%.

When Sis were born

Half of everyone ever recorded as Si was born before 1998 — so the typical Si is around 27 today.

Median birth year
1998
About 27 years old
Biggest decade
2010s
23.5% of all use
Born in the last 25 years
54.8%
A modern name
Recorded since 1950
148
People you could plausibly meet
Choose a decade

2010s — 23.5% of all recorded uses (39).

Is Si rising or falling?

Rank movement and count movement can disagree — the number of distinct names in use keeps growing, so a name holding a steady count still slides down the list. Both are shown.

Rank vs 1 year ago
—
Not ranked then
Rank vs 5 years ago
New entry
Not ranked then
Rank vs 10 years ago
—
Not ranked then
Births vs 10 years ago
—
Not published both years
Share of its own peak
0%
Peak was 2013 (15)
Years since peak
12
Years
Year-to-year steadiness
Volatile
42.0% average annual change
Best rank ever
#2,931
1934

Where Si is used — girls

Across 1910–2025, Si was most concentrated in New York — about 1 in — girls, against 1 in 1,136,945 across all states with data.

00 per 100,000

Most concentrated

  1. 1New York1 in —

Shading is the share of that state's recorded girls given this name, not the raw count — otherwise the map would just show which states are biggest. Unshaded states have no published records for this period. U.S. birth records suppress state-year counts below 5; state counts therefore don't add up to the national total. Every state links to its full rankings. Si has too little recent state data to map, so this covers all years from 1910.

Si around the world

Where Si ranks in official birth records elsewhere in the world. Rankings only — the number of births isn’t comparable between places, so it isn’t shown.

  • England & Wales
    2000–2017
    #4,812
    in 2017
  • France
    1958–2016
    #6,693
    in 2016
  • Canada
    1997–2014
    #1,791
    in 2014
  • South Australia
    1979–2011
    #784
    in 2011

Popularity data from Office for National Statistics, Institut national de la statistique et des études économiques, Statistics Canada and Consumer and Business Services (South Australia). ONS data under Open Government Licence v3.0. INSEE data under Licence Ouverte / Etalab 2.0. StatCan data under Statistics Canada Open Licence. CBS SA data under CC BY 4.0.

Si by the numbers

The raw record for each sex the name is used for.

As a boy's name

Rank in 2025
Unranked
Trend vs 5 yrs ago
—
Best rank ever
#2,931
1934
Peak year
2013
15 that year
First recorded
1927
Last recorded
2017
All-time count
166
Count in 2025
Under 5

As a girl's name

Rank in 2025
Unranked
Trend vs 5 yrs ago
—
Best rank ever
#13,180
2011
Peak year
2011
8 that year
First recorded
2006
Last recorded
2011
All-time count
19
Count in 2025
Under 5

Names similar to Si

Matched on shared beginnings and endings, similar length, and comparable popularity.

SiaosiSianSidiSiamSimsSieSiarSimbaSiahSilerSiyonSirisSilusSiddhSinaSinaiSiloSirusSionSigSirrSinanSirSiyan

Sibling names for Si

Names from the same era and popularity tier — the two things that make a sibling set feel deliberate — skipping lookalike spellings and shared initials.

Explore around Si

Top names of 2013, Si's peak yearThe 2010s in fullOther names that peaked in 1934Boys' names starting with S