f-prot foofoo forrot forton fotron ftroop n-toon noforn non-no non-op nonono nonoon nonpro noonoo noonor noonto noroff noroof norton notfor notron notton nottoo offton ofpoor oftfor on-off onfoot oofotr oooooo oporto optfor optoro oroton ottoor ponton poopoo popfor popoff popopo poporo poppop poptop porno- porron portof porton potron potton pottop pppppp profor pronto proto- proton ronnon ronron rootof rooton rotton to-fro to-on toforn tonono tonoro tonpon tonton tootoo topoff toppop topton tororo torpor tortor totnor totopo totoro totrot tronto tropo- troppo trotro