There defination to sable used in the line is...
Firmly fixed
" And draws the firm;y fixed curtains of the night,"
Legitimacy of the source.
Bod was a child who lived among the ghosts, an outsider of the world. He was inbetween the "dead" and the living, defining him as just about "nobody," because he was neither dead or living.
He was also a loner from when he was a toddler, that made him an isolated child from the rest of the world.
A. To have peace and quiet