"Passed away" is one of the most common euphemisms for "died" in modern American English. According to the Oxford English Dictionary, phrasal verbs such as "pass away," "pass onward," and "pass hence" have been used as synonyms for "die" since the 14th century. The earliest usages refer to the life or soul leaving the body, but by the 18th century, "passed away" definitely meant "died."
Yet, I have not seen very many New England epitaphs that say that the deceased "passed away." The earliest example I can find is from 1866:
It seems possible that "passed away" may not have been in common usage in New England before the 19th century. By the time New Englanders started using the phrase (mid 19th c.?), they were writing shorter epitaphs that often recorded vital dates without any verbs at all.
I don't know why this might be, though. The OED finds the phrase in all the major works of English literature (Chaucer, Shakespeare, etc.) and it's used several times in the King James Bible. Admittedly, most of the Biblical usages refer to physical movement, but there are enough death-related verses that I would expect people who know 101 ways to say died to pick up on them:
- Job 34:20 — In a moment shall they die, and the people shall be troubled at midnight, and pass away: and the mighty shall be taken away without hand.
- Psalms 78:39 — For he remembered that they were but flesh; a wind that passeth away, and cometh not again.
- Ecclesiastes 1:4 — One generation passeth away, and another generation cometh: but the earth abideth for ever.
- Luke 21:32 — Verily I say unto you, This generation shall not pass away, till all be fulfilled.