  We extend our recent computation of the low-energy limit of the linear O(4)
Quark-Meson Model. The present analysis focuses on the transformation of the
resulting effective action into a nonlinearly realized effective pion action,
whose higher-derivative interaction terms are parametrized by so-called
low-energy couplings. Their counterparts in the linear model are determined
from the Functional Renormalization Group flow of the momentum-dependent
four-pion vertex, which is calculated in a fully O(4)-symmetric approximation
by including also momentum-dependent {\sigma}{\pi} interactions as well as
{\sigma} self-interactions. Consequently, these higher-derivative couplings are
dynamically generated solely from quark and meson fluctuations, initialized at
a hadronic scale. Despite our restriction to low-energy degrees of freedom, we
find that the qualitative features of the fluctuation dynamics allow us to
comment on the range of validity and on appropriate renormalization scales for
purely pionic effective models.
