Here's what rhymes with couldst.
wouldst Words that almost rhyme with couldst
cooked accursed bulked accurst wolfed put looked foot pushed hooked booked soot hoofed yurt bushed mooched woofed afoot caput smooched recooked clubfoot unhooked overcooked precooked crowfoot webfoot overlooked congruent occiput overbooked underfoot pussyfoot splayfoot tenderfoot