During the time of the Messenger of Allah ﷺ, when the muadhin would call the adhan, we would think it was the iqamah because of how many people stood up to pray two units of prayer before Maghrib.
حدثنا محمد بن بشار حدثنا محمد بن جعفر حدثنا شعبة قال سمعت علي بن زيد بن جدعان قال سمعت
إن كان المؤذن ليؤذن على عهد رسول الله ﷺ فنرى أنها الإقامة من كثرة من يقوم فيصلي الركعتين قبل المغرب
[Sahih] Ahmad narrated it: 3/282, from Muhammad bin Jafar, with this chain. Ali bin Zayd has already been mentioned, h: 116, and his hadith has sahih corroborating narrations in Bukhari, h: 625, and others similar to it.