Heel
At the foot of the neck
The heel is the portion of the neck that attaches to the body, and curves downward away from the fingerboard:
This "pointy" guitar neck heel is often called a "French heel."
Here's a flat heel on a modern Jazz guitar:
Banjo necks have heels, but they're not as deep as a guitar's:
That's because most neck heels extend the full depth of the body.
This neck has no heel!