Shihtzu sits at #498 with 243 entries, leaning male. This is almost certainly a paperwork artifact — Shih Tzu (or Shih-Tzu) is a breed name, and most of these registrations are owners using the breed as the recorded name on licensing forms, either casually or because the form was filled in fast. The collapsed spelling (no space, no hyphen) is a clue.
The breed-name-as-pet-name pattern
Licensing systems regularly catch breed words being used as call names. Shih Tzu shows up the same way Shiba, Husky, Beagle, and Poodle occasionally appear as registered names. Some owners genuinely call their dog Shihtzu; others wrote it on the form because the dog is a Shih Tzu. The data cannot distinguish the two cases.
The Mandarin lineage
The breed name itself comes from the Mandarin 獅子 (shīzi), meaning "lion," referring to the lion-like coat the breed was bred to resemble. The Shih Tzu has Tibetan and Chinese imperial-court origins going back centuries, with the modern breed standardized in the 20th century. Used intentionally as a call name, it works only on a Shih Tzu — the name is functionally locked to the breed.
Sound counter-reading
The two-syllable shape (SHIH-tzoo) is short and projects well, but the spelling without space or hyphen reads as informal even by pet-name standards. Households would normally settle on a separate call name for daily use. The Shih Tzu breed name page shows the actual top picks for the breed, and the trending pet names list shows the broader rotation.