possible

Re: up as far as possible.

I believe “possible”, meaning the unmentionable, was used before 1921. My mother, born 1896, told of a family joke that she and her sisters thought very funny. A woman went to the doctor feeling ill. The doctor prescribed a long, soaking bath. The woman returned in a week, still feeling ill.

Dr: Did you take a bath?

Woman: I washed up as far as possible and down as far as possible.

Dr: You better go home and wash possible.

I think my aunts were giggling over this before the turn of the century.