Jamieson, Fausset and Brown on Ezekiel 26:15-21

15-21. The impression which the overthrow of Tyre produced on other maritime nations and upon her own colonies, for example, Utica, Carthage, and Tartessus or Tarshish in Spain.

isles--maritime lands. Even mighty Carthage used to send a yearly offering to the temple of Hercules at Tyre: and the mother city gave high priests to her colonies. Hence the consternation at her fall felt in the widely scattered dependencies with which she was so closely connected by the ties of religion, as well as commercial intercourse.

shake--metaphorically: "be agitated" (Jr 49:21).