Sunday is a day-of-the-week name with a specific quality that Monday through Saturday can't match: it carries light, rest, and the particular sweetness of a day that belongs to no institution. Nicole Kidman and Keith Urban named their daughter Sunday Rose in 2008, and the name has been slowly gaining ground on both children and pets ever since.
The Day-Name Difference
Among day names, Sunday is uniquely appealing because it functions differently from Monday through Saturday in cultural meaning — it's the day of sun, rest, family, and (in secular use) of long brunches and slow afternoons. A dog named Sunday carries all of that easy, warm energy. The name works especially well for pets adopted on a Sunday, or for dogs whose personality is defined by a gentle, unhurried contentment.
Celebrity and Cultural Placement
Kidman and Urban's Sunday Rose placed the name in serious conversation, and celebrity usage tends to trickle into pet naming within a few years. Owners who considered Sunday for a daughter and held back often give it to a female pet instead — the same impulse, a different recipient. Golden retrievers and light-colored, mellow-tempered breeds collect this name most often.
Abstract Quality, Concrete Sound
Sunday is three syllables that feel like two in practice — the middle syllable nearly disappears in fast speech. It carries beautifully outdoors and shortens to Sunny when warmth is the priority. The human name context at Sunday covers its trajectory from novelty to genuine consideration. Compare Sunny for a name that covers the same emotional territory with less syllabic weight.