: a tropism in which contact especially with a solid or a rigid surface is the orienting factor
borrowed from German Thigmotropismus, from Greek thígma "touch" (from thig-, base of thingánō, thingánein, aorist éthigon, thigeîn "to touch, handle, take hold of" —of uncertain origin— + -ma, resultative noun suffix) + German -o--o- + -tropismus-tropism
The term was introduced by the German physiologist Max Verworn (1863-1921) in Psycho-physiologische Protisten-Studien (Jena, 1889), p. 90. — Greek thingánein has been compared with Indo-European *dhi-n-ǵh-, evident in Latin fingere "to mold, fashion, make a likeness of" (see feign), a present tense derivative of *dhei̯ǵh- "knead, shape." However, this requires that voiced aspirates would lose aspiration and retain voicing after nasals in Greek, which appears not to be the case.