pageable.messages.itemsPerPage String (default: "items per page"),

The label that is displayed after the drop-down list for the page size.

Example - setting the label after the drop-down list for the page size

<div id="treeList"></div>
<script>
    $("#treeList").kendoTreeList({
        columns: [
          { field: "id" },
          { field: "name" }
        ],
        dataSource: {
            data: [
              { id: 1, parentId: null, name: "item 1" },
              { id: 2, parentId: 1, name: "item 2" },
              { id: 3, parentId: 1, name: "item 3" },
              { id: 4, parentId: 1, name: "item 4" },
            ]
        },
        pageable: {
            pageSizes: [2, 5],
            input: true,
            messages: {
                itemsPerPage: "data items per page"
            }
        }
    });
</script>