Isaac vs Theo
Isaac and Theocompared on official birth-registration statistics and Namewise's recorded data. This page states what each name's record shows — it never picks a winner or scores one name against the other.
Head to head
Ranks are only compared within one published list and one year. Two ranks from different years, from a boys' and a girls' list, or from different registrars are not comparable, so they are not placed side by side.
Scotland · Boys
In 2024, Isaac was ranked #49 and Theo #4 among boys in Scotland.
Northern Ireland · Boys
In 2024, Isaac was ranked #26 and Theo #5 among boys in Northern Ireland.
England and Wales · Boys
In 2024, Isaac was ranked #37 and Theo #12 among boys in England and Wales.
New Zealand · Boys
In 2023, Isaac was ranked #46 and Theo #19 among boys in New Zealand.
Republic of Ireland · Boys
In 2025, Isaac was ranked #104 and Theo #21 among boys in Republic of Ireland.
Norway · Boys
In 2025, Isaac was ranked #251 and Theo #22 among boys in Norway.
New South Wales, Australia · Boys
In 2025, Isaac was ranked #26 and Theo #32 among boys in New South Wales, Australia.
Isaac and Theo over time
Isaac and Theo appear together in 5 published lists, across 125 years of shared records. Isaac held the stronger position in more years in 4 of them, Theo in 1.
The order between them changed and held in 5 of those lists — a change in that published list, never a claim that one name displaced the other.
Isaac reached its own highest recorded position earlier in 5 of those lists, and Theo in none. Each position is a place inside its own list, so this compares when they peaked and never how high.
Counted list by list. Two names in the same published list are measured on the same scale in the same year, so those comparisons are real — but positions from different lists are not, so nothing here is combined into an overall standing.
How this pair is related
The relationship kinds these two qualify for, each under its own stated rule. Every one is drawn from a list they both appear in.
- One took the other's place near the top
In New Zealand · Boys, Theo moved into the top 50 at #35 in 2020 as Isaac fell out of it to #51, having been #36 the year before.
- One moved ahead of the other
In 2017, Theo moved ahead of Isaac in England and Wales · Boys — #20 and #29 the year before became #24 and #21.
- Closest over the longest run
Across 29 shared years in England and Wales · Boys, Isaac and Theo averaged 42.5 places apart, ending at #37 and #12.
- Longest-running competitions
Isaac and Theo were both ranked in Norway · Boys for 34 years, from 1986 to 2025, ending at #251 and #22.
- Peaked in the same years
Both reached their highest recorded position in Northern Ireland · Boys within 2 years — Isaac #20 in 2020, Theo #4 in 2022.
List by list
Norway · Boys34 shared years, 1986–2025
Isaac held the stronger position in 5 of those years, Theo in 29.
Highest recorded here: Isaac #164 in 2014, Theo #17 in 2024.
The order changed in 1997: Theo moved ahead. In 1996 they stood at #450 and #563; by 1997 that had become #568 and #541.
Most recent shared year, 2025: Isaac #251, Theo #22.
England and Wales · Boys29 shared years, 1996–2024
Isaac held the stronger position in 21 of those years, Theo in 8.
Highest recorded here: Isaac #20 in 2015, Theo #9 in 2022.
The order changed in 2017: Theo moved ahead. In 2016 they stood at #20 and #29; by 2017 that had become #24 and #21.
Most recent shared year, 2024: Isaac #37, Theo #12.
Republic of Ireland · Boys29 shared years, 1996–2025
Isaac held the stronger position in 20 of those years, Theo in 9.
Highest recorded here: Isaac #77 in 2014, Theo #13 in 2024.
The order changed in 2017: Theo moved ahead. In 2016 they stood at #98 and #106; by 2017 that had become #84 and #73.
Most recent shared year, 2025: Isaac #104, Theo #21.
Northern Ireland · Boys23 shared years, 2001–2024
Isaac held the stronger position in 16 of those years, Theo in 7.
Highest recorded here: Isaac #20 in 2020, Theo #4 in 2022.
The order changed in 2018: Theo moved ahead. In 2017 they stood at #24 and #48; by 2018 that had become #33 and #18.
Most recent shared year, 2024: Isaac #26, Theo #5.
New Zealand · Boys10 shared years, 2014–2023
Isaac held the stronger position in 6 of those years, Theo in 4.
Highest recorded here: Isaac #28 in 2014, Theo #19 in 2023.
The order changed in 2020: Theo moved ahead. In 2019 they stood at #36 and #44; by 2020 that had become #51 and #35.
Most recent shared year, 2023: Isaac #46, Theo #19.
Two names moving past each other in a ranking is a fact about the ranking. Namewise does not claim one name displaced the other, that families chose between them, or that either influenced the other — none of that is in this data.
Side by side
| Field | Isaac | Theo |
|---|---|---|
| Record type | Editorially researched profile | Editorially researched profile |
| Gender usage | male | male |
| Meaning | Traditionally understood as 'he will laugh' or 'he laughs', tied to the biblical narrative in which Abraham and Sarah laugh at the prophecy of Isaac's birth in their old age. | Gift of God. |
| Origin | Biblical Hebrew, transmitted into English via Greek Isaak and Late Latin Isaac | Greek, via Theodore/Theodora |
| Pronunciation | /ˈaɪzək/ | /ˈθioʊ/ |
| Syllables | 2 | 1 |
| Common variants / nicknames | Not yet recorded | Teddy |
| Recorded regional usage | AU-NSW, GB-ENW, GB-NIR, GB-SCT, IE, NO, NZ | AU-NSW, GB-ENW, GB-NIR, GB-SCT, IE, NO, NZ |
| Most recent popularity observation | New South Wales, Australia · Boys #26 (2025) | Republic of Ireland · Boys #21 (2025) |
| Pronunciation clarity (demonstration score) | 90/100 | 90/100 |
| Spelling simplicity (demonstration score) | 94/100 | 95/100 |
| International familiarity (demonstration score) | 100/100 | 100/100 |
| Data Confidence | medium | high |
What the data shows
- Isaac is recorded with a Biblical Hebrew, transmitted into English via Greek Isaak and Late Latin Isaac origin, while Theo is recorded with a Greek, via Theodore/Theodora origin.
- Isaac has 2 syllables, compared with 1 for Theo.
- Isaac's recorded meaning differs from Theo's — see the table above for each.
- Both names have recorded usage in AU-NSW, GB-ENW, GB-NIR, GB-SCT, IE, NO, NZ.
- The available evidence gives Isaac a "medium" Data Confidence level and Theo a "high" level — this reflects how complete and corroborated the underlying evidence is, not a judgement of either name.
How each name got here
Isaac
Popularity journey
First recorded1964
First recorded at #232 among boys in Republic of Ireland in 1964 — the earliest year that source publishes this name, not necessarily the earliest it was used.
Republic of Ireland · Boys
Highest recorded1990–2025
Highest recorded position: #8 among boys in New South Wales, Australia, in 2015 (recorded 1990–2025).
New South Wales, Australia · Boys
Most recent2025
Most recently recorded at #26 among boys in New South Wales, Australia, in 2025.
New South Wales, Australia · Boys
Theo
Popularity journey
First recorded1986
First recorded at #637 among boys in Norway in 1986 — the earliest year that source publishes this name, not necessarily the earliest it was used.
Norway · Boys
Highest recorded2001–2024
Highest recorded position: #4 among boys in Northern Ireland, in 2022 (recorded 2001–2024).
Northern Ireland · Boys
Most recent2025
Most recently recorded at #32 among boys in New South Wales, Australia, in 2025.
New South Wales, Australia · Boys