to understand; to be convinced; to be satisfied
internal organ; viscera; gut
to lose one's energy; to be cowardly
coward; namby-pamby; wimp; weak-kneed person; spineless person
lungs; bottom of one's heart; vital point
good-for-nothing; spineless; gutless; spiritless; feckless; pluckless
cannot understand; doesn't make sense; unconvincing; hard to swallow; doesn't ring true