[From Latin obstreperus, noisy, from obstrepere, to make a noise against : ob-, against; see ob- + strepere, to make a noise (of imitative origin).] ob·strep'er·ous·ly adv., ob·strep'er·ous·ness n.
1600, from L. obstreperus "clamorous," from obstrepere "drown with noise, oppose noisily," from ob "against" + strepere "make a noise," from PIE *strep-, said to be imitative.