The formal and semantic relationship between λευγαλέος and λυγρός is correct, as both words belong together although none is directly derived from the other.

A point remains uncertain: this explanation appears together with the etymology of λυγρός as a compound of ὑγρός "moist". Λευγαλέος was explained by some in Antiquity as meaning "liquid", and glossed δίυγρος, because of Il. 21.281 where λευγαλέῳ θανάτῳ refers to a death by drowning (see λευγαλέος / λοιγός). Does that imply an intermediate step λυγρός, in which case the etymology would be old because the use of λευγαλέος "liquid" is already attested in Sophocles? That is, the reasoning would be: "λευγαλέος comes from λυγρός, λυγρός comes from ὑγρός, therefore λευγαλέος means "watery", and this is exactly the Maning in Il. 21.281". However, λευγαλέος is never associated with λυγρός in Homeric scholarship.