I have not come across that name but did a little research and found the birth of Mabel. Please see: https://familysearch.org/pal:/MM9.3.1/TH-266-11558-51808-93?...
, in Northampton MA. I will continue to search.
Found an Alonzo Tacy the son of Abram Tacy and Julie Hart born in 1882 in Northampton. I'm pretty sure this is the same. And the Abram Tacy fits into the family of Abraham Tessier/Tacy and Rosalie Luck (the sister of my ancestor). https://familysearch.org/pal:/MM9.3.1/TH-266-11858-130330-62...
If we could find the marriage of Alonzo and Gertrude it would help not sure it may have taken place in VT as she is from that area.
I will do some more searching at a later date.