birth; lineage; parentage; origin
identity; background; history; past
provenance; origin
素性を隠して組織に潜り込んでいた。
He had hidden his background and infiltrated the organization.
素性のわからない人物に注意が必要だ。
You need to be cautious around people whose background is unknown.
彼女の素性を調べたら名家の出身だとわかった。
When I looked into her background, I found she came from a distinguished family.