"He appointed the twelve: Simon [to whom he gave the name Peter]; 17 James the son of Zebedee and John the brother of James [to whom he gave the name Boanerges, that is, Sons of Thunder];". ESV. My emphasis.
Barnes' Notes on the Bible says, "It is not known why this name was given to James and John".
In nature I understand:
A. Thunder can be loud.
B. Thunder may betoken the destruction which lightening can cause.
C. Thunder, which is a sound, travels not as fast as light.
Can we say if Jesus called James and John a name which means "Sons of Thunder" because:
A. They were loud?
B. Their preaching or lives connected to judgement? ["From the throne came flashes of lightening and rumblings and peals of thunder". Rev 4:5].
C. As thunder follows after lightening so they too would follow "the Light"?
John 8:12 "Again Jesus spoke to them saying, "I am the light of the world. Whoever follows me will not walk in darkness, but will have the light of life".