Literally meaning: “inner fluid”
Origin: Anc Greek
ενδο-/endo-(compining form that denotes: inside, internal, within)
νύμφη/nymphi(=in Greek Mythology, nymphs are minor female deities protectors of springs, mountains, and rivers). Nymph via Latin passed as lympha (“water, water nymph”).
Endolymph is the fluid inside the membranous labyrinth of the inner ear.