the use of borrowed images
Images come upon elsewhere acquire a new resonance in Eliot's context --

"Frisch weht der Wind  
 Der Heimat zu.  
 Mein Irisch Kind,  
 Wo weilest du?"

"Od' und leer das Meer"
-- or lend a reaffirming note -- to Eliot's notion of "death by water", for instance, as in this image from Shakespeare:
"Those are pearls that were his eyes"
-- and sometimes, as here, a host of allied images chime in -- 
"Full fathom five thy father lies;       
 Of his bones are coral made;           
 Those are pearls that were his eyes:  
 Nothing of him that doth fade
 But doth suffer a sea-change
 Into something rich and strange.       
 Sea-nymphs hourly sing his knell."