553 names in this catalogue begin with A, and 214 of them run to three syllables or more. Across the whole catalogue only 2,226 names do, out of far more. A is the long letter, and everything else about it follows from that.
Long, and therefore thinner
The letter averages 65 registrations per name. The catalogue averages more. That is the length penalty showing up as a property of an initial: Athena, Amelia, Apollo and Aurora are grand names and grand names are shared by fewer animals.
159 of the letter classifies elegant-sounding, which on this site is another way of saying the same thing — the elegant tag reads length before it reads anything else.
A opens and closes it
157 of these names also end in -a. Ava, Anna, Athena, Aria. No other letter turns back on itself like this, and it is the reason A leans female: 205 measure female against 200 male, in a catalogue that leans the other way.
The short end of it
If the length is the problem rather than the letter, 168 of these are four letters or fewer — Ace, Ava, Abby, Arlo. That is where the A names people actually use are concentrated, and where Archie and Alfie sit just above.
What are good pet names starting with A?
The list above is ordered by how many animals in eleven public registers carry each name, so the top of it is the evidence-backed answer and it updates whenever a register is recounted.
Why do so many A names sound formal?
Because they are long. 214 of the 553 names starting with A have three syllables or more, roughly twice the rate of the catalogue overall, and length is most of what the elegant tag measures.
Are A names more often female?
Slightly: 205 female against 200 male. The ending is doing it — 157 of them finish on the same open vowel they start with.
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.