Bolt and Himawari were both named after Neji, to honour his memory.
Neji literally means 'Bolt', and seeing as Naruto's son has a Bolt as his necklace you can imply it carries both meanings, Bolt as in Neji and Bolt, as in Lighting (To honour Minato, the yellow lighting).
Himawari also means 'Sunflower', which is the meaning of Neji and Hinata's last name, Hyuuga.