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1770+ Boy Names Ending in O

Pamela Redmond
By Pamela Redmond
Updated Sun Sep 29 2024
1770+ Boy Names Ending in O

Boy names ending in O offer many intriguing options, from such top names as Theo to unique O-ending names from Kylo to Zino.

Mateo is the most popular boy name ending with O right now, though there are nearly 100 O-ending boy names among the US Top 1000. Along with Mateo, other boy names in the US Top 1000 include Leo, Santiago, Diego, Romeo, and Antonio.

And there are hundreds more unique names for boys that end with the letter O worthy of your consideration. These range from the biblical Jethro to the ancient Greek Cosmo to the cool, modern Rio and Po.

Here are all Nameberry’s boy names that end with the letter O, ordered by their current popularity on Nameberry.

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  1. Mateo

    • Origin:

      Spanish

    • Meaning:

      "gift of God"

    • Description:

      Mateo is a Latinate name that like Mia and Luca, is becoming popular far beyond its native Spanish community. With its fresh feel and charm, it made a surprise entrance to the boys' Top 10 in 2023.
  2. Milo

    • Origin:

      Latin and Old German

    • Meaning:

      "soldier or merciful"

    • Description:

      Milo is most commonly considered to be Germanic name derived from the Latin word miles, meaning "soldier." However, there is evidence to suggest it also may have independently spawned from the Slavic root milu, meaning "merciful." Milo predates brother name Miles, a variation that evolved when the name immigrated to the British Isles in the Middle Ages. Mylo is an alternate spelling.
  3. Arlo

    • Origin:

      Irish or English

    • Meaning:

      "between two hills"

    • Description:

      Quirky cool Arlo is now well and truly back. Last year it broke into the US Top 200 boy names and consistently ranks among the most popular boy names on Nameberry.
  4. Leo

    • Origin:

      Latin

    • Meaning:

      "lion"

    • Description:

      Leo is a strong-yet-friendly name that was common among the Romans, used for fourteen popes, and is now at its highest point ever in the US thanks in part to Leonardo "Leo" DiCaprio.
  5. Hugo

    • Origin:

      Latinized form of Hugh

    • Meaning:

      "mind, intellect"

    • Description:

      Hugo, the Latin form of Hugh, has more heft and energy than the original -- and of course we love names that end (or begin, for that matter) with an o. This one is especially appealing because it's backed up by lots of solid history and European style.
  6. Elio

    • Origin:

      Italian, Spanish

    • Meaning:

      "sun"

    • Description:

      Elio is a sunny and spirited Italian and Spanish name that makes a great crossover prospect, which could catch on as Enzo has. Elio is also currently popular in France, ranking in the Top 250.
  7. Otto

    • Origin:

      German

    • Meaning:

      "wealthy"

    • Description:

      Otto is cool again. Long a quintessential Old Man Name, Otto has been promoted to trending darling of adventurous baby namers.
  8. Nico

    • Origin:

      Italian diminutive of Nicholas, Greek

    • Meaning:

      "people of victory"

    • Description:

      Nico is one of the great nickname names, full of charm, energy and effortless cool -- a neo Nick.
  9. Enzo

    • Origin:

      Italian variation of Henry, German

    • Meaning:

      "estate ruler"

    • Description:

      You may be surprised to know that Enzo is now a Top 100 boy name in the US and the UK, where it has been climbing straight uphill since the turn of this century.
  10. Theo

    • Origin:

      Diminutive of Theodore

    • Meaning:

      "gift of God"

    • Description:

      See the popularity graph below for the name Theo? It's been heading straight uphill since 2010, when it hopped back onto the Top 1000 after a 60+ year absence.
  11. Cosmo

    • Origin:

      Italian, English, Greek

    • Meaning:

      "order, beauty, universe"

    • Description:

      With a touch of celestial power, a hint of clunky charm, and the totally cool -o ending, Cosmo may well be finally shaking itself free of both the Seinfeld association (which made it a punchline of a joke) and the cartoon fairy association from The Fairly OddParents. In fact, it is in the Top 1000 in the UK and a favorite on Nameberry.
  12. Niko

    • Origin:

      Finnish variation of Nichoals; diminutive of Nikolaos, Greek

    • Meaning:

      "victory of the people"

    • Description:

      Popular in Croatia, Spain, New Zealand, and Slovenia, Niko has also been rising up the US popularity charts for boys since the late 2000s. Fresher than Nicholas, spikier than Nico, it currently ranks just outside the US Top 300.
  13. Ivo

    • Origin:

      German

    • Meaning:

      "yew wood, archer"

    • Description:

      Ivo is an unusual, catchy name with the energetic impact of all names ending in 'o'. Hardly heard in the U.S., it is used a bit more frequently in England, as is the related Ivor, a favorite of such novelists as Evelyn Waugh and P.G. Wodehouse. Ivo is currently most popular in the Netherlands.
  14. Matteo

    • Origin:

      Italian

    • Meaning:

      "gift of God"

    • Description:

      This attractively energetic Italian version of the classic Matthew is primed to move further and further into mainstream American nomenclature. Mateo is technically the Spanish version, but many parents in the US use the two spellings interchangeably.
  15. Orlando

    • Origin:

      Italian variation of Roland

    • Meaning:

      "famous throughout the land"

    • Description:

      Orlando, the ornate Italianate twist on the dated Roland, with a literary heritage stretching back to Shakespeare and before, has appealing book-ended o's, and is open to combination with almost any last name, a la British actor, Orlando Bloom.
  16. Apollo

    • Origin:

      Greek mythology name

    • Meaning:

      "destroyer; strength; father's light"

    • Description:

      With mythological names rising, the handsome son of Zeus and god of medicine, music, and poetry among many other things might offer an interesting, and melodic option. Similar in style to Atlas and Atticus and similar in sound to Arlo, Paolo, Paul, and Ollie, Apollo entered the US Top 1000 back in 2012, and was propelled upwards after it was chosen by Gwen Stefani and Gavin Rossdale in 2014.
  17. Rio

    • Origin:

      Spanish, Portuguese, Japanese

    • Meaning:

      "river; place of the cherry blossoms"

    • Description:

      Rio is a reductive ranchero place-name with an attractive Tex-Mex lilt. No Doubt's Tom Dumont has a son named Rio Atticus.
  18. Viggo

    • Origin:

      Scandinavian

    • Meaning:

      "war"

    • Description:

      Though to most Americans Viggo is a one-person name attached to intense actor Mortensen, it is actually an old Norse name dating back to the Vikings, and is currently the 32nd most popular appellation in Sweden. Viggo Mortensen is a Jr., sharing his name with his Danish father.
  19. Cato

    • Origin:

      Latin

    • Meaning:

      "all-knowing"

    • Description:

      Cato conjures up images of ancient Roman statesmen and southern antebellum retainers; it could have revival potential, with its 'O' ending and the current interest in the names of Greek and Roman antiquity.
  20. Emilio

    • Origin:

      Spanish and Italian variation of Emil

    • Meaning:

      "rival"

    • Description:

      Dashing and suave, with a hint of poetry and gentleness, Emilio is an appealing and international choice. A solid favorite in Italy, it is also on the rise in the US, France, Austria, and the UK.