1660s, "body fluid," from Latin latex (genitive laticis) "liquid, fluid," probably from Greek latax "dregs," from PIE root *lat- "wet" (cf. Middle Irish laith "beer," Welsh llaid "mud, mire," Lithuanian latakas "pool, puddle," Old Norse leþja "filth"). Used 1835 to mean "milky liquid from plants." Meaning "water-dispersed polymer particles" (used in rubber goods, paints, etc.) is from 1937. As an adjective by 1954, in place of clasically correct laticiferous.
latex la·tex (lā'těks')
The colorless or milky sap of certain plants, such as the poinsettia, that coagulates on exposure to air.
An emulsion of rubber or plastic globules in water, used in adhesives and synthetic rubber products.