rainless

Etymology tree
Proto-Indo-European *Hréǵʰ-der.
Proto-Indo-European *Hréǵʰnos?
Proto-Germanic *regną
Proto-West Germanic *regn
Old English reġn
Middle English reyn
English rain
Proto-Indo-European *lewh₁-
Proto-Indo-European *lewHs-der.
Proto-Germanic *leusaną
Proto-Germanic *lausaz
Proto-Germanic *-lausaz
Proto-West Germanic *-laus
Old English -lēas
Middle English -les
English -less
English rainless
From rain + -less.