diff --git a/Core/HardParticle/FormFactorPolyhedron.cpp b/Core/HardParticle/FormFactorPolyhedron.cpp
index 56dbe632383c238313e814d8637011f675bf2616..eb092056084e83ee15aaf30b3aa3ae912f69be7a 100644
--- a/Core/HardParticle/FormFactorPolyhedron.cpp
+++ b/Core/HardParticle/FormFactorPolyhedron.cpp
@@ -421,11 +421,11 @@ void FormFactorPolyhedron::setLimits(double _q, int _n)
 
 //! Called by child classes to set faces and other internal variables.
 
-void FormFactorPolyhedron::setPolyhedron(const PolyhedralTopology& topology, double z_origin,
+void FormFactorPolyhedron::setPolyhedron(const PolyhedralTopology& topology, double z_bottom,
                                          const std::vector<kvector_t>& vertices)
 {
     try {
-        m_z_origin = z_origin;
+        m_z_bottom = z_bottom;
         m_sym_Ci = topology.symmetry_Ci;
 
         double diameter = 0;
@@ -472,12 +472,12 @@ void FormFactorPolyhedron::setPolyhedron(const PolyhedralTopology& topology, dou
     }
 }
 
-//! Returns the form factor F(q) of this polyhedron, respecting the offset z_origin.
+//! Returns the form factor F(q) of this polyhedron, respecting the offset z_bottom.
 
 complex_t FormFactorPolyhedron::evaluate_for_q(cvector_t q) const
 {
     try {
-        return exp_I(-m_z_origin * q.z()) * evaluate_centered(q);
+        return exp_I(-m_z_bottom * q.z()) * evaluate_centered(q);
     } catch (std::logic_error& e) {
         throw std::logic_error("Bug in " + getName() + ": " + e.what()
                                + " [please report to the maintainers]");
diff --git a/Core/HardParticle/FormFactorPolyhedron.h b/Core/HardParticle/FormFactorPolyhedron.h
index 0b575727991c93b9b053e397f04557c9fd23e9ec..3c61a11e723992eeeb7dcab19dd867f0acceae9c 100644
--- a/Core/HardParticle/FormFactorPolyhedron.h
+++ b/Core/HardParticle/FormFactorPolyhedron.h
@@ -116,10 +116,10 @@ public:
     void assert_platonic() const;
 
 protected:
-    double m_z_origin;
+    double m_z_bottom;
     bool m_sym_Ci; //!< if true, then faces obtainable by inversion are not provided
 
-    void setPolyhedron(const PolyhedralTopology& topology, double z_origin,
+    void setPolyhedron(const PolyhedralTopology& topology, double z_bottom,
                        const std::vector<kvector_t>& vertices);
 
 private:
diff --git a/auto/Wrap/doxygen_core.i b/auto/Wrap/doxygen_core.i
index 4443aaaea83bf5e30943039e044dae6173868207..197cecb221ec1ea504962e7adf90d7be8563a6ae 100644
--- a/auto/Wrap/doxygen_core.i
+++ b/auto/Wrap/doxygen_core.i
@@ -4350,7 +4350,7 @@ C++ includes: FormFactorPolyhedron.h
 
 %feature("docstring")  FormFactorPolyhedron::evaluate_for_q "complex_t FormFactorPolyhedron::evaluate_for_q(cvector_t q) const override final
 
-Returns the form factor F(q) of this polyhedron, respecting the offset z_origin. 
+Returns the form factor F(q) of this polyhedron, respecting the offset z_bottom. 
 ";
 
 %feature("docstring")  FormFactorPolyhedron::evaluate_centered "complex_t FormFactorPolyhedron::evaluate_centered(cvector_t q) const
diff --git a/auto/Wrap/libBornAgainCore.py b/auto/Wrap/libBornAgainCore.py
index dfc4e8df16c5e4bb0df0ffd05e7eaf0f0b704ea6..0f0ff976ab68d26b1da32a6ddcac94aa4efab7be 100644
--- a/auto/Wrap/libBornAgainCore.py
+++ b/auto/Wrap/libBornAgainCore.py
@@ -9381,7 +9381,7 @@ class FormFactorPolyhedron(IFormFactorBorn):
         evaluate_for_q(FormFactorPolyhedron self, cvector_t q) -> complex_t
         complex_t FormFactorPolyhedron::evaluate_for_q(cvector_t q) const override final
 
-        Returns the form factor F(q) of this polyhedron, respecting the offset z_origin. 
+        Returns the form factor F(q) of this polyhedron, respecting the offset z_bottom. 
 
         """
         return _libBornAgainCore.FormFactorPolyhedron_evaluate_for_q(self, q)
diff --git a/auto/Wrap/libBornAgainCore_wrap.cpp b/auto/Wrap/libBornAgainCore_wrap.cpp
index d4e6afc7c20a0f842f4e3d0e85f52751cf1628cb..8a0a4d7994d0cee9467bbb91840c5bcf4a87945d 100644
--- a/auto/Wrap/libBornAgainCore_wrap.cpp
+++ b/auto/Wrap/libBornAgainCore_wrap.cpp
@@ -126735,7 +126735,7 @@ static PyMethodDef SwigMethods[] = {
 		"FormFactorPolyhedron_evaluate_for_q(FormFactorPolyhedron self, cvector_t q) -> complex_t\n"
 		"complex_t FormFactorPolyhedron::evaluate_for_q(cvector_t q) const override final\n"
 		"\n"
-		"Returns the form factor F(q) of this polyhedron, respecting the offset z_origin. \n"
+		"Returns the form factor F(q) of this polyhedron, respecting the offset z_bottom. \n"
 		"\n"
 		""},
 	 { "FormFactorPolyhedron_evaluate_centered", _wrap_FormFactorPolyhedron_evaluate_centered, METH_VARARGS, "\n"