This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
佖 combines 亻 (person) with 必, but the historical origin and original meaning are uncertain.
A person 亻 beside 必, but the meaning is unclear. Think of it as a person with an unknown purpose.
For ヒツ, imagine a person 亻 hitting 必 with a stick: hits -> ヒツ, though the meaning remains uncertain.