Here's what rhymes with iotum.
erratum Words that almost rhyme with iotum
button mutton piton sudden glutton dudgeon nubbin dubbin exciton globin bludgeon unbutton scutcheon escutcheon androgen bellybutton custom caecum accustom buxom buncombe bunkum dumdum cementum humdrum jejunum corundum secundum colostrum conundrum carborundum