3. To do one's business / doing one's business , means to defecate or, more rarely, to urinate. Usage dates back to the 17 th century. See defecation and urination for synonyms.
(1) Lawyer (Donn Whyte) and Xaviera Hollander (Joey Heatherton) at the Senate Committtee on 'Sexual Excesses in America' in The Happy Hooker Goes to Washington (1977): -- Lawyer: ' Please state for the committee your business.' -- Xaviera: ' Pleasure.'
(2) Lady Flavia (Ann-Margret) to Général Pêcheur (Henry Gibson) in The Last Remake of Beau Geste (1977): ' It's been a business doing pleasure with you.'