It is a common linguistic phenomenon that the most frequent expressions of a language get shorten or reduced to one word over time. By their very nature, this is the case with many greetings.
- Ciao = from the Venetian: S-cià o tuo / I'm your slave
- Arrivederci = A ri-vederci / to see us again
The word ‘good-bye’ comes from the 16th-century word ‘godbwye’, which is a shortened form of ‘God be with ye’.— Quite Interesting (@qikipedia) August 9, 2020
See ya ;) !