Sir ranks at #276 with 413 entries, and it is one of the most deliberately ironic names on the chart. The honorific functions as a name precisely because the contrast between the formality and the chaos of an actual dog is the entire joke.
The title-as-name pattern
Sir clusters with Duke, Prince, King, and Captain in the title-name register. Most of these names carry their meaning straight (a Duke that acts noble), but Sir is different because it is almost never used straight — Sir is the punchline, and the dog is small or scruffy or otherwise unsirly.
The official-name reading
Sir often shows up as a prefix to a longer formal name, the kind owners write on the registration paperwork for purebred dogs: Sir Reginald, Sir Barksalot, Sir Wigglebottom. The shortened call-name then becomes Sir in everyday use. That pattern accounts for a meaningful share of the chart entries here.
Sound and the counter-reading
The single-syllable shape (SUR) is short and sharp, but the open vowel limits its carrying power compared to harder-ending one-syllable names. The name lands well across breeds because the joke works on almost any dog, though small dignified breeds — French Bulldogs, Pugs, Cavaliers — over-index slightly. The Sir baby name page shows it has effectively never been a meaningful human pick, which is part of why it reads so cleanly as a pet name.