Lyric discussion by FloydianTheory 

Cover art for Scream Thy Last Scream lyrics by Pink Floyd

The "genius" here is the shocking weirdness and dark horror merged with childhood whimsy and toddler rhymes. Some of those lyrics were sung because he liked the cadence and flow of those words together. There's probably no inherent meaning other than an image of childhood strangeness, a fleeting memory of a toy, a book, or whatever. Floyd took this to a whole other dimension after Syd was out of the band. You hear the fright and terror in songs they did post-Syd like Careful With That Axe, Eugene and One Of These Days. It crops up in songs like Sheep and several places on The Wall too.

My Interpretation