Boys names ending in o

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.

Calixto is known in Spain as the name of three popes, one of whom was the martyr, Callixtus I, regarded as a saint. Calixto has a lot of energy and futuristic spirit, thanks in part to the attention-grabbing 'x.' He is the main character in the Spanish classic, Fernando de Rojas's Tragicomedy of Calixto and Melibea.

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.

Indigo is one of the most appealing and evocative of the new generation of color names. Color names have joined flower and jewel names -- in a big way -- and Indigo, a deep blue-purple dye from plants native to India, is particularly striking for both girls and boys. Although most people don't think of it like this, Indigo might also be considered among the most stylish Greek baby names in use today. Some cultural references: The Indigo Girls are a folk duo, 'Mood Indigo' is a classic Duke Ellington jazz composition, and there is a 1970's New Age theory that Indigo children possess special, sometimes supernatural abilities. Indigo is the name of a character in the Ntozake Shange novel Sassafrass, Cypress & Indigo, and was used for his daughter by Lou Diamond Phillips.

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.

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

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

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.