to look at closely, nearsighted, dim, indistinct vision
瞀 centers on impaired or strained vision: looking closely but seeing dimly, being nearsighted, or having indistinct sight.
瞀 combines 目 (eye) with 敄, which likely contributes the sound. The character is associated with impaired vision, but the exact historical development of 敄 is uncertain.
The top part 敄 looks like a tangled mess, and the bottom 目 is an eye. Imagine trying to peer through a tangled thicket: your vision becomes dim and nearsighted.
For ボツ, imagine a nearsighted person bumping into things with a soft 'botsu' sound: botsu -> ボツ, as they squint and stumble.