late 14c., "type of facial ulcer, lupus," from L., lit. "touch me not," from noli, imperative of nolle "to be unwilling" + me (see me) + tangere "to touch" (see tangent). Used over the years of various persons or things that must not be touched,
esp. "picture of Jesus as he appeared to Mary Magdalene" (1670s) and "plant of the genus Impatiens" (1560s, so called because the ripe seed pods burst when touched).