Personalities of the Buddhist Suttas
Kumāra-kassapo Kassapa The Boy
DPPN: He was foremost among those who had the gift of varied and versatile discourse (cittakathikanam). His mother was the daughter of a banker of Rajagaha, and she, having failed to obtain her parent's consent to become a nun, married and, with her husband's consent, joined the Order, not knowing that she was with child. When her condition was discovered her colleagues consulted Devadatta, who declared that she was no true nun. The Buddha, on being consulted, entrusted the matter to Upali, who had it fully investigated by Visakha (Migara's Mother) and other residents of Sāvatthī, and he gave his finding in the assembly, in the presence of the king, that the nun was innocent. When the boy was born the king reared him, and the boy was ordained at the age of seven.
From the Psalms [brackets are translator's]:
All hail the Buddhas, and all hail the Norms.
Hail the blest System by our Master wrought,
Wherein he that doth hear may [be enrolled
And] come to realize a Norm like ours.
Down countless ages have its members come,
Reborn now as this compound, now as that.
But this for them is now the very last,
The final confluence [of the factors five,]
In flux of rebirth and mortality.
Now come they never more again to be.
DPPN: [Vammīka Sutta]: According to the Commentary, Kumārakassapa was not an arahant at the time of the preaching of the sutta. The diety was a deity of the Suddhāvāsa-brahma world. He was one of five friends who, in the time of Kassapa Buddha, had entered the Order and who, in order to meditate uninterruptedly, had climbed a rock by means of a ladder which they had then removed, thus cutting off their return. The eldest became an arahant in three days, the second (anuthera) was this deity, who had become an anāgāmī. The third was Pukkusāti, the fourth Bāhiya Dārueīriya and the last Kumārakassapa. This deity was responsible for the arahantship both of Bāhiya and Kassapa, for Kassapa took the Vammīka Sutta as the subject of his meditations and thus developed insight.
Cittakathikanam. As per Woodward; can't really do better, could be: 'who shines at speaking'.
MA. I. 340