1
general::
Phrase(s): pass away [and] pass on
Euph. to die. • My aunt passed away last month. • When I pass on, I won’t care about the funeral.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
Also, pass on or over. Die, as in He passed away last week, or After Grandma passes on we'll sell the land, or I hear he's about to pass over. All these terms are euphemisms for dying, although the verb pass alone as well as pass away have been used in the sense of "pass out of existence, die" since the 1300s. The two variants?? adding on [c. 1800] and over [c. 1900]allude to moving to some other-worldly realm.
American Heritage Idioms