The first Rash"i in Masechet Taanis (20a) says that Nakdimon Ben Gurion's real name was Boni. How did Rash"i know that, is there any earlier source for that?
A little further down the daf (about half way, Taanis 20a)
תָּנָא לֹא נַקְדִּימוֹן שְׁמוֹ אֶלָּא בּוּנִי שְׁמוֹ וְלָמָּה נִקְרָא שְׁמוֹ נַקְדִּימוֹן שֶׁנִּקְדְּרָה חַמָּה בַּעֲבוּרוֹ
A Sage taught: Nakdimon was not his real name; rather his name was Buni. And why was he called Nakdimon? Because the sun broke through [nikdera] for him.