To be in complete agreement. This term, from the second half of the 1900s, alludes to reading from the same page of a book. It has largely replaced the earlier on the same wavelength, which alluded to the radio waves of a broadcast and dates from the first half of the 1900s. The newer version appears in David Baldacci’s Hour Game (2004), “We need to coordinate and keep each other informed. We all need to be on the same page.”