This is the 4204th most frequent Japanese word.
久保田
"久保田" (Kubota) is a Japanese surname or place name.
In this sentence, 久保田 is used as a proper noun referring specifically to a person named Kubota, indicated by the honorific さん.
久保田さんは新しい仕事を始めました。
Mr. Kubota has started a new job.
Here, 久保田 refers to the name of a brewery, illustrating its use as a brand or institutional name.
私は久保田酒造の日本酒が好きです。
I like the sake from Kubota Brewery.
In this example, 久保田 represents the name of a restaurant, showing its usage as a designation or title for an establishment.