<type name="ExampleFooModelFoo">
    <arguments>
        <argument name="stuff" xsi:type="array">
            <item name="hello" xsi:type="string" translate="true">Hello World!</item>
        </argument>
    </arguments>
</type>

namespace ExampleFooModel;

class Foo {
    public function __construct(array $stuff = [])
    {
        var_dump($stuff);
    }
}