Didn't match

וישמע הכנעני מלך ערד ישב הנגב *    Rashi explains that it was actually עמלק who was ישב הנגב but disguised himself, by speaking in the language of  כנען so to confuse the Yidden when they will Daven to Hashem to save them from the enemy כנען instead of עמלק Since they  wore Amaleiki clothing the Yidden realized something doesn't make sense and Davend without mentioning any name of the enemy. The Kalir in the Piyut of Shabbos Parshas Zachor writes זכור יושב הנגב בלי על כערד כסות ולשון שנה Seems that the Kalir holds (unlike Rashi) that he changed both, his clothing and also his language. The (מהרש"א (ר"ה ג ע"א  says that we can say that the Kalir & Rashi are not arguing. The meaning of כסות ולשון שנה is that the כסות didn't match the לשון since he wore Amaleiki clothes and spoke Kanani language. (like Rashi) *Bamidbar 21:1