FAQ 10: Why the name ‘Ekklesia’?
The Greek word ekklesia refers to a people's assembly within the public square. It also has strong Hebrew roots to denote 'peoplehood', and is a key New Testament term for the practice (rather than the institutionalisation) of ‘church’, reminding Christians of the inescapably political nature of their existence – in other words, summoning them as followers of Jesus Christ to a fresh form of social life based on mutuality rather than self-aggrandizement.
Our friend Professor Deirdre Good has some additional comments to offer in 'Specifying the "ekk^lesia"' - http://www.ekklesia.co.uk/node/5961/
See also "Democracy, 'ekklesia' and the church: a movement for change" - http://www.ekklesia.co.uk/node/21171
The Roman word ecclesia is more associated with hierarchical, Christendom forms of church, whereas Ekklesia is seeking to explore post-Christendom possibilities for Christian community, purpose and witness.
“The New Testament ekklesia was an extended family unit and communitarian, where everyone shared everything with everybody”, comments Victor Choudhrie.