Carcassonne has historically used the term "pennant" to refer to the shield icons in cities but now appears to use the term "coat of arms". They both do the same thing (add two points to completed cities and one point to uncompleted cities). When did this name change happen?
The original German is Wappen.
English rules have translated that variously as Pennant, Banner, Shield, or Coat of Arms.
The Rio Grande edition called it Pennant. The Z-Man edition called it Banner. And when Z-Man printed "Carcassonne II" (art by Pätzke instead of Matthäus), they called it Coat of Arms.
From the German forum:
Das Wappen in dem Stadtgebiet:
Carcassonne (Grafik bei Doris Matthäus)
Bei RioGrandeGames: pennant
Bei ZmanGames: banner
Carcassonne II (Grafik bei Anne Pätzke)
Bei ZmanGames: coat of arms
So the change "from" pennant came in 2012 with ZMG 78000. That changed it to "Banner". The change from "banner" to "coat of arms" came in 2014 with ZMG 78100.
Carcassonne moved from being distributed by Rio Grande Games to Z-Man games in 2012. Here's a quote from a June 2012 The Gaming Gang article :
Hans im Gluck announced that they will be using a new distributor for the English releases of their games. Their partnership with Rio Grande is coming to an end, and by this fall/winter you will only be able to purchase Carcassonne and all its variations from Z-Man Games.
This came with several accompanying changes, including an update to the art style on the box and tiles, as well as some terminology changes is the rules. This is likely when the change in terminology from "pennant" to "coat of arms" occurred.
From the 2014 Z-man rules (emphasis is mine):
Each tile in a completed city is worth 2 points.In addition, each coat of arms is worth 2 more points.
From the 2006 Rio Grande rules (emphasis is mine):
A player who has a knight in a completed city scores 2 points for every city segment. Every pennant scores an extra 2 points.