There was a time in my career where a wise mentor encouraged me to steer away from object types that ended in "er". He had observed that when people used these names, it was often a code smell and the underlying object had been put together to "do" a thing. And that it was better to strive for names that better described what the thing was. Subtle at times. And there are words in the english language that end in er, but have become synonymous with related nouns.
In Kotlin, which is a "multi paradigm" language, I'm not sure this advice applies though. That advice came in the context of the world of Smalltalk, where it was turtles^H^H^H^Hobjects all the way down. I still find though, that I tend to steer clear (but not asbolutely avoid) "er" objects.