Conversation so far:
What is the etymology of vlachs?
The word "Vlach" is etymologically derived from the ethnonym of a Celtic tribe, adopted into Proto-Germanic *Walhaz which meant "stranger".
Why were the considered strangers?
signify "stranger, foreigner" also in the Balkans, where it in its early form was used for Romance-speakers, but the term eventually took on the meaning of "shepherd, nomad".
Was it considered derogative?
In Croatia, the term became derogatory, and Vlasi was used for the ethnic Serb community.
Was it ever not meant in a derogatory way?
CANNOTANSWER.
Is there anything else interesting about the etymology of this word?
Romanian scholars have suggested that the term Vlach appeared for the first time in the Eastern Roman Empire and was subsequently spread.

Question: Who first coined the term?
Self-contained rewrite: Who first coined the term Vlach?