O holds only 194 names, which puts it near the bottom of the alphabet by size. It averages 85 registrations each, which puts it near the top by use. Few names, heavily carried — and 87 of them measure male against 42 female, the sharpest lean of any small letter.
Oreo, Ollie, Otis, Ozzy, Oscar
The top of the letter is a single shape repeated: two syllables, opening on the vowel, closing on something bright. Oreo alone accounts for a striking share of the letter's whole weight, which is what happens when a small list contains one name everybody knows.
Why it reads male
An initial O is nearly always followed by a hard consonant in English — Otis, Oscar, Ozzy, Odin — and the vowel-then-stop opening is one this catalogue reads as male throughout. The letter has very few soft-opening options to balance it, because English gives it very few.
Short, and almost no long ones
84 of the letter is four letters or fewer. There is nowhere else for these names to go: a word starting with a bare O and running to eight letters is rare in English generally, and the register data reflects the language rather than any choice owners made.
What are the most popular pet names starting with O?
Oreo leads by a distance, then Ollie, Otis, Ozzy and Oscar. The ordering is by registration count across eleven public registers.
Are O names mostly male?
Strongly: 87 male against 42 female. An initial O is nearly always followed by a hard consonant, and that opening reads male throughout this catalogue.
Why are there so few O pet names?
194 of them. English has few given names or nouns starting with a bare O, so the letter is small everywhere and not only here — but the ones it has are used heavily, at 85 registrations each.
Every count on this site is a tally of real registrations: pet licences and shelter intakes published as open data by New York, Seattle, Austin, Montgomery County, Cambridge, Zurich, Basel and four Australian councils. Popularity here is the average share a name holds across those registers, so a name common in a small city is not buried by one common in a large one. Five of the eleven registers are North American and they supply 86% of the records, so read the ordering as naming in those places rather than worldwide. Browse the whole catalogue or read how the data is put together.