to make a great effort
伮 centers on exerting oneself fully: making a great effort or striving hard.
伮 combines 亻 (person) with 奴, which likely contributes the sound. The exact historical development is uncertain, but the character likely expresses a person exerting effort.
A person 亻 beside 奴, which resembles someone working hard. Picture a person straining and putting in great effort.
For ド, imagine a person making a great effort to push a heavy door: door -> ド, and the person strains against it.