At the end of Parashat Bo (Exodus 13:14), Rashi enumerates the Four Sons of the Passover Seder:
דברה תורה כנגד ארבעה בנים, רשע ושאינו יודע לשאול והשואל דרך סתומה והשואל דרך חכמה
The Torah spoke regarding four sons: the wicked one (Exod. 12:26), the one who does not understand to ask (Exod. 13:8), the one who asks [a] general [question], and the one who asks in a wise manner. — [from Yerushalmi, Pes. 10:4]
(Emphases mine. References inserted by chabad.org.)
We (like the Yerushalmi Rashi apparently draws from) refer to the wise son simply as "wise son." Why does Rashi refer to him as "the one who asks in a wise manner"?