Newtonian rhymes with:
plutonian, bostonian, estonian, houstonian, plutonian, washingtonian, amazonian, andonian, apollonian, babylonian, bostonian, caledonian, devonian, draconian, estonian, gorgonian, houstonian, jacksonian, jeffersonian, melkonian, oregonian, patagonian, plutonian, simonian, smithsonian, usoniam, washingtonian
Newtonian sounds like:
nadein, nadine, nandaime, natan, nathan, nathania, nathene, nation, natuna, nayden, needham, neoteny, netan, netanyahu, newton, newtown, newtowne, nineteen, nodine, nomination, noontime, notation, nothin, nothin', notion, nowotny, nutone, nydam