Immemorial rhymes with:
memorial, memorial, memorial, morial, advertorial, ambassadorial, arboreal, conspiratorial, correale, curatorial, dictatorial, directorial, editorial, equatorial, extraterritorial, flonorial, gubernatorial, janitorial, memorial, morial, nomenclatorial, pictorial, professorial, prosecutorial, raptorial, reportorial, sartorial, senatorial, territorial, tutorial