score:2
The Sutta Nipata source is Sn-A 3.10:
Roman Pali:
http://tipitaka.org/romn/cscd/s0505a.att2.xml
Sinhalese Pali:
http://tipitaka.org/sinh/cscd/s0505a.att2.xml
The relevant passage is:
Atha kho brahmā sahampatīti ko ayaṃ brahmā, kasmā ca bhagavantaṃ upasaṅkamitvā etadavocāti? Ayaṃ kassapassa bhagavato sāsane sahako nāma bhikkhu anāgāmī hutvā suddhāvāsesu uppanno, tattha naṃ ‘‘**sahampati brahmā’’ti sañjānanti.
අථ ඛො බ්රහ්මා සහම්පතීති කො අයං බ්රහ්මා, කස්මා ච භගවන්තං උපසඞ්කමිත්වා එතදවොචාති? අයං කස්සපස්ස භගවතො සාසනෙ සහකො නාම භික්ඛු අනාගාමී හුත්වා සුද්ධාවාසෙසු උප්පන්නො, තත්ථ නං ‘‘සහම්පති බ්රහ්මා’’ති සඤ්ජානන්ති.
Roughly:
"And then the Brahma Sahampati" - Who was this brahma? And from what [cause] did he, having approached, say this? This one, a bhikkhu named Sahaka in the sasana of the Kassapa the Blessed One, having become an anagami, arose in the Pure Abodes; there, they knew him as "Sahampati Brahma".