Hawari
Yes, the plural form Hawariyun appears in Surah Al-Imran 3:52 referring to the disciples of Prophet Isa (Jesus).
It means 'disciple,' 'pure-hearted companion,' or 'devoted follower,' derived from the Arabic root for purity and whiteness.
No, it is extremely rare in modern usage, though historically attested in early Islamic records.
Traditionally it is masculine, though the concept of devotion is universal. Most Islamic jurisprudence recommends it for boys.
It represents the ultimate loyalty and spiritual purity exemplified by the disciples who supported Prophet Isa.