Audacious comes from the Latin root audere (dare) audac-/audax ("bold") and came to English in the mid 15th century. Shakespeare used "audacious" seven times in his plays. That in itself wasn't exactly an act of bold originality.  It had been around for decades.  

If you look up the word “audacious” in Webster's Thesaurus, however, you'll see that it has several, very different connotations. One, as it relates to words like courageous, heroic, and gallant, and another is the audacity synonymous with impudence, temerity, or brazenness. 

The word audacity was first used in English in the Middle English period, around 1432–50 in Higden's Polychronicon.  It comes from the Latin word audacitas, which means "boldness". 

Examples of audacious in a sentence: