The word feisty was derived from the word noun "feist," a term that can be traced back to the 1500s for a small, aggressive dog.  It comes from a Middle English verb fysten or fisten, which means "to fart" or "to stink" and was used in the phrase "fysting curre," meaning "stinking dog". 

According to the Oxford English Dictionary (OED), the earliest recorded use of "feisty" was in 1875, appearing in American Agriculturist.  It is an American English adjective formed by adding the suffix "-y" (meaning "like" or "full of") to "feist" (primarily a noun meaning a small ill-tempered dog).  "Feisty" describes someone who is spirited, lively, and courageous, often with a determined and independent attitude.

Examples of "feisty" used in a sentence: 
"The novel features a feisty heroine." 
"Even her opponents admire her feisty spirit."
"Winds will be feisty out of the south around 10 to 15 mph." 
"Emily is a feisty woman fighting for her rightful inheritance." 
"I like her attitude - she's really feisty, she digs in and doesn't give up." 
"Elizabeth Bennett is feisty, intelligent, sharp, even sly, mysterious, and a nineteenth century version of sarcastic." 
"I am the proud mom of a feisty two year old little girl, and I balance my time between her and my private practice in Westchester County, NY." 

Just the facts:

FEISTY Definition & Meaning - Merriam-Webster

FEISTY Synonyms: 103 Similar and Opposite Words | Merriam-Webster Thesaurus

The Etymology of “Feisty” – Useless Etymology