Idk, feels like my brain does not have the model for this, this does not exist in my language afaik haha.
Replace opt with its equivalent “choose” and it becomes choose-(tobe-)in and choose-(tobe-)out.
Opt-in = "we assume you are out unless you tell us you want to be in"
Opt-out = "we assume you are in unless you tell us you want to be out"
Just remember, good company’s leave them off by default. Bad companies will turn them on for you.