Nodal-line resonance generating the giant anomalous Hall effect of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Co</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:msub><mml:mi>Sn</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">S</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>

Giant anomalous Hall effect (AHE) and magneto-optical activity can emerge in magnets with topologically nontrivial degeneracies. However, identifying the specific band-structure features such as Weyl points, nodal lines, or planes which generate response is a challenging issue. Since low-energy interband transitions govern static AHE, we addressed this question prototypical magnetic semimetal ${\mathrm{Co}}_{3}{\mathrm{Sn}}_{2}{\mathrm{S}}_{2}$ also hosting lines by broadband polarized reflectivity Kerr spectroscopy focus on far-infrared range. In linear dichroism spectrum observe strong resonance at 40 meV, appears optical conductivity primarily determines thus confirms its intrinsic origin. Our material-specific theory reproduces experimental data remarkably well shows that strongly tilted nodal-line segments around Fermi energy resonance. While points only give vanishing contributions, these of gapped spin-orbit coupling dominate giant AHE.