ismur : shower
The Illunse word for shower is ismur. Ismur is an rare last name. In Spain ISMUR is an acronym for Iniciativa Social de Mujeres Rurales (Rural Women's Social Initiative).
This word is a mixture of the the Latin word imber (rain, storm, shower of water/snow/hail/missiles) and the Old English word scúr (shower, tempest, storm of rain, snow, hail, shower of blows).
This is the current word for shower.
I couldn't find a Quenya or Sindarin word for shower.
ismuras : showers
The Illunse word for showers (nominative plural) is ismuras. Similar Ismarus is a Greek city or island in the "The Odyssey".
Showers in Latin is imbris. Showers in Old English is scúras.
The plural, showers, is new.