prepared
僃 centers on being ready or prepared. The given meaning is straightforward, but this is a rare kanji with limited usage.
僃 is a rare variant of 備. The exact historical development is uncertain, but it likely shares the same origin as 備, which combines 亻 (person) with a phonetic component.
A person 亻 standing by with everything needed, ready to act: 僃 means prepared.
For ビ, imagine a person being prepared: 'be' ready -> ビ.