The word is possibly a portmanteau from Latin sylvestris and nympha, sylvestris being a common synonym for sylph in Paracelsus. Anthon and Trollope note a similar usage in the Aeneid, where silvestris is taken as an elliptical form of nympha silvestris (" forest nymph"). Jacob Grimm uses this phrase as a gloss for the Anglo-Saxon wudu-mær (roughly equivalent to "woodmare"), which he also takes as a metaphorical name for an echo. Jan Baptist van Helmont, a near contemporary of Paracelsus and coiner of the word "gas", uses sylvestris in the sense of "wild" to describe gaseous emissions, which may be connected to the Paracelsian usage. Thorpe's Northern Mythology connects the adjective sylvestres and the related silvaticas to European wild man legends. A related idea is that "sylph" is from a hyper-urbane respelling of a Latin neologism silves, but in either case this connection to the Latin root silva (" forest ") is supported by Paracelsus' use of sylphes as a synonym for schrötlein, a German word for a tree spirit or especially an earth spirit in his Liber de Sanguine ultra Mortem.An alternative theory is that it derives from the Ancient Greek σίλφη (silphē), which a number of etymological sources gloss as "moth", though the most authoritative reference for Ancient Greek, A Greek–English Lexicon, is unaware of this sense and defines it as a "cockroach" or " book worm". French etymological sources often derive it from a Latin word sylphus, glossed as "genius" (in the Latin sense, a type of spirit ) and only known from inscriptions rather than literary Latin. The Deutsches Wörterbuch however indicates that this idea arises from a 19th-century misreading of the inscription in question.