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I will discuss a novel mechanism for generating (QCD) axion dark matter that is particularly relevant at low axion decay constant where experiments are sensitive. Rather than coming from the energy initially stored in the zero-mode axion background field, the dark matter
energy density comes from the fluctuations of the axion field that are induced by primordial (inflationary) curvature perturbations. Such a source term is effective if the background scalar field has a large kinetic energy, as well-motivated in rotating axion models. These fluctuations can explain the totality of dark matter in a vast axion parameter space, particularly for the QCD axion, which will be targeted by upcoming experiments. I will review the conditions on this mechanism
and the comparison with axion dark matter from the kinetic misalignment mechanism.