Expositor's Bible Commentary Commentary Acts 2:7

"And they were all amazed and marvelled, saying, Behold, are not all these that speak Galilaeans?" — Acts 2:7 (ASV)

Galileans had difficulty pronouncing gutturals and had the habit of swallowing syllables when speaking; so they were looked down upon by the people of Jerusalem as being provincial (cf. Mark 14:70). Therefore, since the disciples who were speaking were Galileans, it bewildered those who heard because the disciples could not by themselves have learned so many different languages.