the foot: the part of the body a person or animal stands and walks on
Across the New Testament this word keeps one plain meaning, the foot, but that one body part is put to work in a striking range of pictures. Many verses simply name the literal foot: a foot that can cause a person to sin and is better lost than kept, the feet a risen Jesus shows to prove he is not a ghost, the feet of a lame man made strong, the shining feet of a heavenly figure.
The rest of the range is idiom built on what feet do and where they sit. To fall, sit, or lay something at another's feet is the body's language of homage, pleading, and devotion, which is why people drop at Jesus' feet for healing and forgiveness, why a woman wets his feet with tears, why money is laid at the apostles' feet, and why Paul says he learned at the feet of his teacher. To put enemies under the feet is the picture of total conquest and rule, the language of the royal psalms that the New Testament applies to Christ. To shake the dust off one's feet is a deliberate sign that a town has been left to its own choice. And the feet sometimes stand for the whole direction of a life, so that feet are swift to shed blood, or beautiful when they carry good news.
These are shades of one concept, not separate words: in every case it is still the literal foot, read for what a foot signals in that setting. A reader who pictures the actual gesture, the body bent low, the foot pressed down on a defeated enemy, the dust struck off at the town gate, will catch the force the New Testament intends.