Where does “A8” come from?

I can't write this etymology summary because the headword "A8" has an unknown meaning, and without knowing what word is being etymologized, I cannot accurately trace its origin or weave in sense development as required. If you could clarify what English word this chain describes (the summary suggests it might be "accession," but you've listed "A8" as the headword), I can write the proper one-sentence origin.

A8 (English): The eight former Eastern European countries that acceded to the European Union in 2004

Definitions

  1. The eight former Eastern European countries that acceded to the European Union in 2004

Ancestry of “A8”, step by step

StepLanguageWordMeaning
1EnglishaccessionA coming to; the act of acceding and becoming...
2Latinaccessioapproach; onset; increase, addition
3Latin-tiōtion, -ation, -ing
4Latindissertātiō(spoken) dissertation, discourse, disquisition
5Latindissertusarranged, disposed; explained
6Latindissereresecond-person singular future passive indicative...
7Latindis-asunder, apart, in two; reversal, removal;...
8Latincalceusshoe
9Latincalxlimestone; chalk; the finish line
10Ancient Greekχάλιξsmall stone, pebble; gravel, rubble
Every word from Ancient Greek χάλιξEvery word from Latin -tiōEvery word from Latin dis-