  It is a general notion that disorder, introduced by either chemical
substitution or intercalation as well as by electron-irradiation, is
detrimental to the realisation of long-range charge-density-wave (CDW) order.
We study the disorder-induced suppression of the in-plane CDW orders in the
two-dimensional Pd-intercalated ErTe$_3$ compositions, by exploring the real
part of the optical conductivity with light polarised along the in-plane $a$
and $c$ axes. Our findings reveal an anisotropic charge dynamics with respect
to both incommensurate unidirectional CDW phases of ErTe$_3$, occurring within
the $ac$-plane. The anisotropic optical response gets substantially washed out
with Pd-intercalation, hand-in-hand with the suppression of both CDW orders.
The spectral weight analysis though advances the scenario, for which the CDW
phases evolve from a (partially) depleted Fermi surface already above their
critical onset temperatures. We therefore argue that the long-range CDW orders
of ErTe$_3$ tend to be progressively dwarfed by Pd-intercalation, which favours
the presence of short-range CDW segments for both crystallographic directions
persisting in a broad temperature ($T$) interval up to the normal state, and
being suggestive of precursor effects of the CDW orders as well as possibly
coexisting with superconductivity at low $T$.
