Brand comes from Proto-Germanic *brandaz,meaning "fire, torch, sword (poetic)." In English, brand only means "torch" and "sword" in literary contexts, unlike its related Germanic cognates which still mean "fire".
His host's given name Kegan is likely based on Old Norse kagi "young tree, shrub", cf. English keg and key ; the surname Rodhe likely from hróðr "glory".
Pyroclasm derives from pyroclastic, a term used to describe fast-moving volcanic material, from Greek πῦρ "fire" & κλαστός "broken"
Kegan Rhode is a bastard son of a magical healer mother and a raider father. He has no memory of his father.
Kegan Rhode was 19 years old when Brand took over his body.
He was 7 when he learned about his magical heritage and abilities.
He was 13 when he met Zvanna.
He was 17 when he parted ways with Zvanna, afterwars she had her own husband and a son.
After the death of his Mother he left the what remained of his village. At the age of 19, Kegan met and became an apprentice to Ryze during one of his trips into the Freljord.
Brand might have been based on the mythical Norse fire giant Surtr "swart(y)": Brand resembles him (blackened skin with lava crackling underneath) and, like Surtr in Ragnarök, Brand is destined to renewing the world by burning it.
Brand occupying the body of seafaring marauder Kegan Rhode might be referencing Human branding, a process in which, for example a slave, was branded a searing mark that would then leave a permanent scar.