where did this "lang" string come from and why?

view/theme/duepuntozero/lang_selector.tpl

@@ -0,0 +1,10 @@
+<div id="lang-select-icon" class="icon s22 language" title="$title" onclick="openClose('language-selector');" ></div>
+<div id="language-selector" style="display: none;" >
+	<form action="#" method="post" >
+		<select name="system_language" onchange="this.form.submit();" >
+			{{ for $langs.0 as $v=>$l }}
+				<option value="$v" {{if $v==$langs.1}}selected="selected"{{endif}}>$l</option>
+			{{ endfor }}
+		</select>
+	</form>
+</div>