Alexander and the Triballoi

Envoys now visited Alexander from all the other autonomous tribes settled near the Danube and from Syrmos, the king of the the Triballoi. Envoys also arrived from the Celts who dwelt on the Ionian Gulf. Men of enormous stature, the Celts had a high opinion of themselves. All the envoys had come desiring Alexander’s friendship, and he exchanged pledges with one and all. He asked the Celts what in the human realm they feared the most, expecting that, since his great name had reached the Celts and gone even farther, they would say they feared him above all. But the Celts’ reply disappointed him. For as they dwelt far from Alexander and inhabited a place that was hard to reach, and as they saw that Alexander’s efforts were directed elsewhere, they said they feared only that the sky might fall on them; and though they admired Alexander, neither fear nor any concern for their advantage had moved them to send these envoys. Alexander declared these men his friends and made an alliance with them before sending them off, though he remarked under his breath, “Big talkers, these Celts!”
(The Landmark Arrian: The Campaigns of Alexander, 1.4.6-8, translation by Pamela Mensch)

Estimated location of Triballoi and other tribes
Picture source, although some liberties may have been taken