The desctiption and name don't seem consistent with what this actually does. None of the parameters are of type `Map` - the map is just an implementation detail. It actually takes metadata from the attributes of an `Element`, and mentioning `Map` makes it take about 10 times as long to figure that out.

We could increase consistency and readability by changing `tuElem` to `fromTuElem`.

Description and method name do not indicate the purpose of `String tmSrcLang`. I'm be forced to read the implementation to figure out what it is for - looks like it is the default source language to use if `tuElem` does not specify one. I would at very least want to see this mentioned in the javadoc, if it can't be made self-evident with naming.