Toidy is baby talk for (that is, a mispronunciation of) the word "dirty." The word is frequently
associated with toilets, child defecation, and, by extension, the genitals. When an infant innocently plays with its feces or genitals, parents may implore the child to stop, saying "Dirty!
That's dirty." The child mimics the parent's word, "dirty," but, lacking full and proper
pronunciation, it sounds like "toidy."