lymph: [17] Despite its Greek appearance, lymph comes, perhaps via French, from Latin. Its distant ancestor was Latin limpa or lumpa, which meant ‘water’. And that was the original sense of English lymph; not until the 18th century was it used for ‘clear bodily fluid’. The alteration of the Latin word to lympha appears to have been due to association with Greek númphē ‘nymph’. English limpid [17] comes from Latin limpidus ‘clear’, which may have been related to limpa.
lymph (n.)
1725 in physiology sense, "colorless fluid found in the body," from French lymphe, from Latin lympha "water, clear water, a goddess of water," variant of lumpæ "waters," altered by influence of Greek nymphe "goddess of a spring, nymph." The word was used earlier in English in the classical sense "pure water, water" (1620s), also (1670s) with reference to colorless fluids in plants. Also see lymphatic. Lymph node is attested from 1892.