Latex
mid 17th century (denoting various bodily fluids, especially the watery part of blood): from Latin, literally ‘liquid, fluid’.
wiktionary
Borrowed from New Latin latex(“clear fluid which is part of a humour or bodily fluid”), a later use of Latin latex(“water; liquid, fluid”). Potentially a borrowing from Ancient Greek λᾰ́τᾰξ(látax, “drop of wine”), reformed by analogy to other nouns in -ex. The semantic shift, however, from drop of wine to water is difficult to explain and may indicate that both words originated from a separate language. Perhaps from the same root as Proto-Celtic *lati- (Old Irish laith(“liquid, beer”), Welsh llad(“beer”)) or Proto-Germanic *ladjō- (Old High German letto(“clay, loam”), Old Norse leðja(“mud, dregs”)) or from a Pre-Greek language. [1] [2] [3]
etymonline
latex (n.)
1660s, "body fluid," from Latin latex (genitive laticis) "liquid, a liquid, fluid," probably from Greek latax "dregs," from PIE root *lat- "wet, moist" (source also of Middle Irish laith "beer," Welsh llaid "mud, mire," Lithuanian latakas "pool, puddle," Old Norse leþja "filth").
From 1835 as "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 the classically correct laticiferous.
