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The handy Latin prefix ob-, meaning "in the way," "against," or "toward," occurs in many Latin and English words, often in alternate forms. Obstreperous comes from ob- plus strepere, a verb meaning "to make a noise," so someone who is obstreperous is literally making noise to rebel against something, much like a protesting crowd or an unruly child. The word has been used in English since around the beginning of the 17th century. Strepere has not played a role in the formation of any other notable English words, but ob- words abound; these include obese, obnoxious, occasion, offend, omit, oppress, and oust.

Examples

After two months at sea with dwindling food supplies and declining confidence in the captain, the ship's crew became obstreperous and began to plot a mutiny.

"It is Rob she calls for when crankily refusing to go to bed, and when Alan attempts to calm her she grows only more obstreperous." — Charles Isherwood, The New York Times, 9 Nov. 2015