The Marx family grew up on the Upper East Side of New York City, in a small Jewish neighborhood sandwiched between Irish/German and Italian neighborhoods. Leonard Marx, the oldest Marx brother, developed the "Italian" accent he used as "Chico" to convince some roving bullies that he was Italian, not Jewish. For a time on Vaudeville all the brothers performed in ethnic accents. Groucho did a German accent. However after the sinking of the RMS Lusitania in 1915 there was anti-German sentiment, and Groucho's "German" character was booed. He quickly dropped the accent and developed the fast-talking wise guy character he would make famous.
Groucho developed a routine as a wise-cracking man with a distinctive chicken-walking lope and an exaggerated greasepaint moustache, improvising insults to stuffy grande dames who stood in his way. He and his brothers starred in a series of movies and stage shows, often departing from the scripts they were working with.
Groucho also worked as a radio comedian and show host in the 1930s and 1940s. In the 1950s, he hosted the popular television program You Bet Your Life. The show consisted of Groucho interviewing the contestants and ad libbing jokes. Then they would play a brief quiz. The show was responsible for the phrases "Say the secret word and win a prize" and "Who is buried in Grant's Tomb?"
Groucho was a master at improvising clever insults, and became well known for this. One of his frustrations in later years was that when he insulted people who annoyed him they tended to laugh, thinking it was just part of the famous comedian's act.