  The charge and spin dynamics of the structurally simplest iron-based
superconductor, FeSe, may hold the key to understanding the physics of high
temperature superconductors in general. Unlike the iron pnictides, FeSe lacks
long range magnetic order in spite of a similar structural transition around
90\,K. Here, we report results of Raman scattering experiments as a function of
temperature and polarization and simulations based on exact diagonalization of
a frustrated spin model. Both experiment and theory find a persistent low
energy peak close to 500cm$^{-1}$ in $B_{1g}$ symmetry, which softens slightly
around 100\,K, that we assign to spin excitations. By comparing with results
from neutron scattering, this study provides evidence for nearly frustrated
stripe order in FeSe.
