This page needs an admission before it needs a list. Until this catalogue was audited, the most registered entries under U were Unknowed, Undecided and Unkown — 601 registrations between them, more than every real U name combined. They are not names. They are what a licensing clerk types when an animal arrives without one, and three spellings of the same word is the proof.
They have been removed
Those rows are rejected now and no longer counted anywhere on this site — not in the letter, not in the totals, not in the popularity bands. The registers are honest data honestly published; the mistake was ours, in treating a free-text field as though every value in it were a name.
It is worth knowing that this class of error exists, because other pet-name sites are built on the same public files and a list showing Unknown as a popular name is a list nobody checked.
What the letter actually holds
63 names, at 21 registrations each — the smallest and thinnest end of the alphabet. Uno, Uma, Una, Ursula, Ulysses. Latin, Spanish and Scandinavian borrowings, mostly, because English has almost no native given names beginning with U.
Short, and split evenly
31 of the letter is four letters or fewer, and 19 measure female against 19 male. With a set this small, treat both figures as description rather than as a pattern — there is not enough here to carry a generalisation.
What are pet names starting with U?
Uno, Uma, Una and Ursula are the most registered. The letter holds only 63 names, so the list above is very nearly all of them.
Why did Unknown appear as a popular pet name?
Because licence registers have one free-text field for the name, and when an animal arrives without one somebody types a status into it. Unknowed, Undecided and Unkown held 601 registrations in this catalogue before they were rejected. Any site built on the same public files without checking will still show them.
Are there many U pet names?
No — 63 in total, the smallest end of the alphabet along with Q and X. English has almost no native given names starting with U, so what is here is mostly borrowed.
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.