Why did C.S. Lewis call his fantasy world Narnia?

Answer 1

Probably because Chronicles are like stories. These children: Peter, Susan, Edward, and Lucy all had stories about going to Narnia and had many adventures there, like chronicles. These adventures took place in Narnia, so he probably named the books because of that.

Answer 2

C.S. Lewis named his fantasy world Narnia after the Italian town Narni, which is believed to have enchanted him as a child. Lewis visited Narni while traveling in Italy and it left a lasting impression on him.

Answer 3

The origin of the name Narnia is uncertain. According to Paul Ford's Companion to Narnia, there is no indication that Lewis was alluding to the ancient Italian Umbrian city Nequinium, which the conquering Romans renamed Narnia in 299 BC after the River Nar. However, since Lewis studied classics at Oxford, it is possible that he came across at least some of the seven or so references to Narnia in Latin literature There is also the possibility (but no solid evidence) that Lewis, who studied medieval and Renaissance literature, was aware of a reference to Lucia von Narnia ("Lucy of Narnia") in a 1501 German text, Wunderliche Geschichten von geistlichen Weybbildern by Ercole d'Este. There is no evidence of a link with Tolkien's Elvish (Sindarin) word narn, meaning a lay or poetic narrative, as in his posthumously published Narn i Chîn Húrin, though Lewis may have read or heard parts of this at meetings of the Inklings.There is no record why he chose (or invented, really), this word as the name of his fantasy land.

-this answer was extracted from wikipedia