so-and-so, one, a certain, that person
某 centers on referring to an unspecified person or thing: a certain someone, so-and-so, or that person when the identity is not stated.
某 combines 甘 (sweet) and 木 (tree), but the historical origin is uncertain. It may have originally referred to a type of plum or fruit tree, later borrowed for the abstract sense of 'a certain person or thing'.
Picture a sweet 甘 tree 木 whose fruit is so rare that people only refer to it vaguely: 'that certain tree' or 'so-and-so's tree'. 某 is that unspecified thing.
For ボウ, imagine pointing at a certain person and saying 'That's Bow!' as if calling them by a vague nickname: Bow -> ボウ, and the person remains unnamed.
certain; one
certain place
a certain person; unnamed person; Mr. So-and-so; a certain someone who shall remain unnamed
certain country
certain company; unnamed company
certain person; certain amount
someone; unknown person
so-and-so
certain day
a certain month
a certain ministry; an unspecified ministry
a certain publication