Wordnet 3.0
NOUN (1)
1. 
 euphemisms for death (based on an analogy between lying in a bed and in a tomb); 
- Example: "she was laid to rest beside her husband"- Example: "they had to put their family pet to sleep"[syn: rest, eternal rest, sleep, eternal sleep, quietus]
WordNet (r) 3.0 (2006):
eternal rest
    n 1: euphemisms for death (based on an analogy between lying in
         a bed and in a tomb); "she was laid to rest beside her
         husband"; "they had to put their family pet to sleep" [syn:
         rest, eternal rest, sleep, eternal sleep,
         quietus]