Thread:BertH/@comment-35399509-20180425014706/@comment-5275700-20180425224832

This involves editing the system messages associated with the user groups. Help:User rights notes the specific message for each group.

However, my suggestion is that you should not do this right now. It can be confusing for new people who are just finding your wiki. You also don't have any content on your wiki and that should really be your focus at this time. Once you have some other people participating, a fun community activity might be voting on the new names.