When Paul wanted a language to talk about the gatherings of the followers of Jesus, he didn't mine his religious heritage for it. Rather he used the vocabulary of the market place.
The word ekklesia (which we translate 'church') was a word used to describe gatherings of all kinds - especially political ones. Famously in Acts 19, the magistrates in Ephesus use the word to describe the riot of the silversmiths (v32, 40) and the gathering of the people in council (v39) - where both times 'assembly' (in the NRSV) is a translation of ekklesia.
Then when Paul uses words to describe leadership, he is infuriatingly fluid in his use of language. Sometimes he speaks of elders (a Jewish leadership word) and sometimes he uses episkopos (the Greek word we get bishop from but which was used in the first century to describe a leader in a voluntary association). Maybe his use is determined by who's reading his words - those of a Jewish background would recognise 'elder' as a leadership word, while those from Gentile background would know 'episkopos' was someone with a leadership role in the community.
Paul seems to have gone out of his way to find language to describe church that his readers would have found familiar from their context. New Testament scholar Andrew Clarke says: 'It is clear that these early Christians were already operating with the expectation that the characteristics of leadership within the Christian ekklesia should parallel those characteristics of leadership in the civic ekklesia'.
But while Paul used familiar language to describe his gatherings and the leadership in them, he spent a lot of time describing how those gatherings should function and how leaders would operate within them. In other words he used familiar words and then gave that language a Christian twist through how he talked of them.
I think the genius of this is that it helped people to feel unthreatened and at home as they came into churches because the words used to describe how things were done were familiar to them. Over time, the meaning of this language was filled out with a particular Christian take on it.
Perhaps we need to learn to use language to talk about membership in our churches today in a similar way.