  Giant anomalous Hall effect (AHE) and magneto-optical activity can emerge in
magnets with topologically non-trivial degeneracies. However, identifying the
specific band structure features like Weyl points, nodal lines or planes which
generate the anomalous response is a challenging issue. Since the low-energy
interband transitions can govern the static AHE, we addressed this question in
the prototypical magnetic Weyl semimetal Co$_3$Sn$_2$S$_2$ also hosting nodal
lines by broadband polarized reflectivity and magneto-optical Kerr effect
spectroscopy with a focus on the far-infrared range. In the linear dichroism
spectrum we observe a strong resonance at 40\,meV, which also shows up in the
optical Hall conductivity spectrum and primarily determines the static AHE,
thus, confirms its intrinsic origin. Our material-specific theory reproduces
the experimental data remarkably well and shows that strongly tilted nodal line
segments around the Fermi energy generate the resonance. While the Weyl points
only give vanishing contributions, these segments of the nodal lines gapped by
the spin-orbit coupling dominate the low-energy optical response.
