ReservedKeywordsResult.cls

public with sharing class ReservedKeywordsResult {
    public String currency_x;
}

reservedKeywordsToObject.dwl

%dw 2.0 
input incomingJson application/json
output application/apex
fun renameKey(key: Key) = key match {
    case "private" -> "isPrivate"
    case "object" -> "obj"
    case "currency" -> "currency_x"
    else -> (key)
}
--- 
incomingJson map (record) -> (
    record mapObject (value, key, index) -> {
        (renameKey(key)) : value
    }
) as Object {class: "ReservedKeywordsResult"}

ReservedKeywordToObject.cls

String jsonString = '[{"currency" : "ABC"}]';

DataWeave.Script script = new DataWeaveScriptResource.reservedKeywordsToObject();
DataWeave.Result result = script.execute(new Map<String, Object>{ 'incomingJson' => jsonString });

List<ReservedKeywordsResult> results = (List<ReservedKeywordsResult>) result.getValue();

System.debug(results);

Assert.areEqual(1, results.size());
ReservedKeywordsResult res = results[0];
system.debug(res);
Assert.areEqual('ABC', res.currency_x);