From the root ك ن س (k n s). In Fraenkel’s and Nöldeke’s view the meaning “to sweep” is from Aramaic כְּנַשׁ / ܟܢܫ (kənaš, “to gather; to sweep”), denominal via مِكْنَسَة (miknasa, “broom”). Note Mehri kənūs (“to sweep”).
Practice speaking and memorizing "كنس" and many other words and sentences in Arabic.