1, 2

I got a rather intriguing word request: why do we say number one for urination and number two for defecation? The short answer is that we don't know, and there are a lot of different theories. I've seen several sketchy internet sources saying that the practice emerged in American classrooms in the 1960s, when children were asked to raise different numbers of fingers when asking to go to the bathroom, so the teacher could know how long the kids would take. While this may have helped popularize the phrase (which really took off in the 1970s), it's actually been around since as early as the 1880s. Other speculatory theories (probably without much merit) are that the phrases are so named because 1 is shorter than 2, because 2 rhymes with "poo", or because you only do 1 thing while peeing and sometimes do 2 while defecating. Basically, we don't know.