To be fair to them, they probably forgot to write it down due to the excitement. Why use a quill to scribble on something when you can stab an eye with it instead? Much more satisfying
There is some truth in this. Many of us have slavic ancestry, especially those in the southeast regions. Myself included, due to my Karelian heritage. In western Finland it's much more rare.
Nevertheless, call us Slavs and there will be blood.
EDIT: Also, interestingly, Paris is named after a Celtic tribe. Celtic isn't Germanic, but normally gets lumped together. Celtic tribes actually predate Germanic ones in what's now France.
Celtic tribes predate Germanic settlement in southern Germany and Austria as well. The Celtic culture also originates in the Hallstatt culture named after a town in Austria where salt mining has been going on since that time.
The Helvetii were also a Celtic tribe in what is now Switzerland.
With Bulgarians it's enough telling them that those ignorant Westerners can't distinguish between Greeks and Thracians. Something similar could work with Romanian about Dacians. With Serbs I don't see this working - it would mean they are Macedonian, and I don't see how they could swallow that.
Serbia and Greece are brotherly nations, both Christian Orthodox suffering under the Ottoman Empire, allied during most wars, etc. The serbians wont like being called greeks but they will hate less than others.
And we can always change it to "romioi", ie "romans"(of the greek variety, Eastern Roman Empire aka Byzantine Empire). The serbians and others in the region would be more cool with that.
Romioi is even used in modern greek(mostly in literature) as equivalent of "greek". Romaioi is the term for the Latin romans.