The first person to accurately describe the origin of the name "The Low Place" was Paul Bazanchuk who correctly noted that The Low Place is “the point on the Holyoke Range where 7 Sisters proper begins”.
If you have run the 7sisters trail race, you may know The Low Place as the brief portion of the trail that you will encounter after coming down from the top of Mount Hitchcock that is actually very runnable. It is also the location of the first/last water stop (water that has to be hauled in by the race staff on foot!) I like to pretend that this portion of the course is named after me even though I am almost certain that it is not.
I am not surprised that Paul B. was got the geographic reference since he lives in Amherst (MA) and The Low Place straddles the town line between the neighboring towns of Hadley and South Hadley. He also wrote a post about his efforts to clean up this portion of the trail following a recent ice storm. Paul B., I owe you a beer. Below is a profile of the 7sisters trail race course with some of the notable hypsographic features labeled.
Or, you you prefer map view, The Low Place can be found on the map of Skinner SP below where the LP (Low Place) trail intersects the M&M trail.