Be meticulous and precise, fill in all the particulars, as in Laura had dotted all the i's and crossed the t's, so she wondered what she'd done wrong . This expression presumably began as an admonition to schoolchildren to write carefully and is sometimes shortened. William Makepeace Thackeray had it in a magazine article ( Scribner's Magazine, 1849): "I have . . . dotted the i's." [Mid-1800s]