How legitimate is it to use the word "festival" for da'wah activities and programs, and is this word permissible or not?

Al-Mahrajan's origin is a festival from the festivals of the Majus (Zoroastrians). Nowruz and Al-Mahrajan are two festivals of the disbelievers. Al-Mahrajan coincides with the seventeenth day of autumn. Therefore, da'wah activities should not be called Al-Mahrajan; instead, they should be called knowledge gatherings (majalis al-'ilm) or similar terms known among Muslims.