I have seen this symbol and similar ones engraved on tombstones in cemeteries in North Andover, MA, as well as around Reading, MA. The tombstones date from the 18th and 19th centuries. Anyone know anything about it?
Indeed it is a willow - generally referred to as a Weeping Willow. I have seen it many times in older cemeteries, both as an engraving and as a living specimen, while helping relatives on genealogy quests. The common explanation seems to be that the Weeping Willow (as its name implies) signifies sorrow and / or loss. A cursory web search seems to support that : HugeDomains.com
Edit - remove .th from the OP’s links to see a decent size
Yes, it’s a weeping willow, sheltering a funerary urn. My family’s been involved in the management of an old city cemetery for many years, and I’ve seen that kind of design before.
My favorite inscription, by a widower for his late wife: “Fifty years with a tongue so sharp - O angels, give her a harp!”