For an AAF from Avid imported into Resolve creating a timeline, the Edit Index "Reel Name" seems to be Avid Master Clip "Source Icon" name metadata. (This is default Resolve behavior if turning on Reel Names. And one can view this everytime if in Resolve there was no media present and one imported the Avid created AAF.)

The "Source Icon" name in the Avid gets embedded into the MXF OP-Atom media file and in Resolve the user extracts reel name based on embedded. Matching metadata is the trick here.

when sending Resolve MXF media files I like to prepare for a return back to Avid too:

Before sending to Resolve, in the Avid Bin, viewed in "Text Mode", with a source activated, looking for an exact same metadata populated in two rows

One row for the source icon name metadata.

An example of what a tapeless "Source File" metadata Master Clip's "Source Icon" looks like in an avid bin when viewed in "Text Mode"

Master Clip's Source Icon has populated metadata in the "Name" column, by default. 

- so far,  I have always seen a master clip have a source icon triggered for display, unless the master clip contained no timecode metadata

One row for the master clip.

These two rows together are the metadata continuity that for most file types has been how I create optimized-reconforms for the idenification of the file to connect. This with matching fps and timecode has been filling the requirements for a lot of file types.

With any of this non-linear, random-access, color correction, finishing, online editorial computer i/o stuff, please always test making sure one is getting the desired results before diving in.

I hope this is helpful!!!