Conversation so far:
What is the etymology of vlachs?
The word Vlach/Wallachian is etymologically derived from the ethnonym of a Celtic tribe, adopted into Proto-Germanic
Why were the Vlachs considered strangers?
Via both Germanic and Latin, the term started to signify stranger, foreigner.

Question: Was it considered derogative?
Self-contained rewrite: Was the term Vlachs considered derogatory?