The word: الْفِرْدَوْسِ (al-Firdaus) in: جَنَّاتُ الْفِرْدَوْسِ (Gardens of Firdaus) means a verdant valley full of fruits and flowers - with reference to Paradise. However, difference exists as to the origin of this word. Is it Arabic, or is it non-Arabic? Those who call it non-Arabic have to refine it further. Is it Persian or Greco-Roman or Syriac? There are different views about this.
It appears in the Sahih of al-Bukhari and Muslim that the Holy Prophet ﷺ said: 'when you ask of Allah, ask for Jannatul-Firdaus because it is the highest and the superior most rank of Jannah. Above it, there is the Throne of the Rahman and from it issue forth all streams of .Jannah.' (Qurtubi)