What does Nathaniel mean?
From Hebrew Netan'el, combining natan 'he gave/given' + el 'God' — 'God has given'. A 'gift of God' name expressed as an act: God has given (this child).
What does Seth mean?
From Hebrew Shet, tied to the verb shat, 'to set, place, appoint.' Genesis 4:25 explains it through Eve's words 'God has appointed (shat) for me another child' — a biblical wordplay that is consistent with the underlying root.