Previously, I had skip/keep but that looked a bit weird in a subscript on the LHS of an assignment, because it replaces the thing you're "keeping". Before that I had skip/next, which reads better, but is slightly odd in the end-relative case, where it means "next to the left". There probably isn't any single word that is totally clear on its own.
If we can cover the basic functionality (and meet the basic requirements) in a straightforward, consistent way, I don't see a problem adding "convenience" API on top that introduces operators for brevity, or uses Python-style signed offsetting. I just wasn't much in favor of those being the only choices.
I believe the ultimate goal is to be able to complete SE-0132.