I noticed today that Google Docs changed their icon on one of their buttons. Clicking this particular button will select the formatting for the current element; you can then click on another element and apply to it the formatting from the first element. Icon designers have long made metaphors between abstract actions and concrete actions, using images from the latter to represent the former. The metaphor for this action has long been painting — applying the formatting feels a bit like you are painting the new element with your mouse — and the icon to represent this action has long has been a paintbrush.
Here are pictures of the two icons:
It struck me that I must no longer consciously think of the metaphor when I use the action; I now just think “paintbrush equals copy formatting.” The new icon sticks with the same metaphor, but I found it a bit jarring because it is now a paint roller instead of a paintbrush. When I didn’t find the paintbrush, only then did I think back to the metaphor and figure out that the paint roller must perform the same abstract action as the paintbrush did.