The other possibility might be found in the Old Irish manuscripts, where all the various heroes and lesser beings meet up either to feast together or to confront each other before the mutual slaughter starts. Somewhere there must be a phase where they greet each other before they go on to identify who they are and show off and brag. But that entails trawling through a lot of text.
Here's Xavier Delamarre presenting his dictionary and he points out that knowledge of the lifestyle of les Gaulois and especially knowledge of their language has increased enormously just over the last thirty years.
http://www.youtube.com/watch?v=4OenyZZRUSwlibrairie mollat