Wiktionary
Etymology 1 interj. (context slang English) An imitation of the sound of gagging, used to express disgust or disdain. vb. (context slang English) To have the vomiting reflex triggered. Etymology 2
n. (lb en Judaism) A metal sheet used to cover stovetop burners on Shabbat to allow food to be kept warm without violating the prohibition against cooking.
Wikipedia
A blech (from the Yiddish word בלעך (blekh) meaning " tin" or " sheet metal") is a metal sheet used by many observant Jews to cover stovetop burners (and for some, the cooker's knobs and dials) on Shabbat (the Jewish Sabbath), as part of the precautions taken to avoid violating the halachic prohibition against cooking on the Sabbath.
Usage examples of "blech".
They seemed to be alive, and if you looked at them long enough, even in process of construction or when they were being torn down and nothing remained but the torso, they were alive in every way: they sprinted along the dike, running figures beckoned, threatened, attacked, thrashed, waved from shore to shore, let themselves be carried by the wind, engaged in conversation with the sun, blessed the river and its fish, counted the poplars, overtook the clouds, broke off the tips of steeples, tried to ascend to heaven, to board or pursue the ferry, to take flight, they were never anonymous, but signified Johann Lickfett the fisherman, Pastor Blech, time and time again Kriwe the ferryman, who stood with his mouth open and his head to one side, Captain Bronsard, Inspector Haberland, or whomever else those lowlands had to offer.