  We use polarization-resolved Raman spectroscopy to study the anisotropy of
the electronic characteristics of the iron-pnictide parent compounds
$A$Fe$_{2}$As$_{2}$ ($A$~=~Eu, Sr). We demonstrate that above the structural
phase transition at Ts the dynamical anisotropic properties of the 122
compounds are governed by the emergence of $xy$-symmetry critical collective
mode foretelling a condensation into a state with spontaneously broken
four-fold symmetry at a temperature $T^{*}$. However, the mode's critical
slowing down is intervened by a structural transition at Ts, about 80~K above
$T^{*}$, resulting in an anisotropic density wave state.
