The piñata is a common Mexican tradition, but it originally comes from China and was supposedly brough to Europe by Marco Polo, and from there to Mexico by Spanish missionaries. Nobunata's samurai styling is a reference to the piñata's origin.
Nobunaga (from which Nobunata's name is derived; see below) is also the namesake of the Nobunaga's Ambition game series, which had a crossover with the Pokémon series.
Nobutata is a popular candidate for the "Audino Pokemon," meaning it is rare but encounterable throughout the region (wandering samurai), as well as being worth above average EXP (beating it and treats bursting out).
Nobunata is based on a donkey piñata, with samurai styling.
Nobunata's name is a combination of Nobunaga (the name of a legendary daimyo, or warlord, in feudal Japan who helped to unite the country) and piñata.