Lady, EVOLVED 
me: gaepora is large and looks like an owl. consequently, people liked to call him “big bird”
you, four chapters later when the realization hits:
@Lady what is the realization
@aescling well, you see, four chapters in is when gaepora’s wife gives birth to zelda
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@aescling the deep lore cut i’m setting up here is that the reason why botw zelda’s mom called her “little bird” (a nickname later adopted by urbosa) was because it was a hereditary nickname stretching back to the first zelda, who was called that just because her dad was a large man with long eyebrows
@aescling that, or botw zelda edited it in to the story, take your pick