The story
From eye + wash. Compare typologically Russian глаз замы́лился (glaz zamýlilsja) (akin to мы́ло (mýlo), мыть (mytʹ)).
Etymology from Wiktionary, CC BY-SA 4.0.
eyewash
Today it means: The washing out of the eyes with copious solution (usually water alone) to quickly remove an irritant, as for example in laboratories and industrial plants; the washing solution itself. Full definition →