Here’s how to override the default template for an input label and make it an actual label, in semantic traditional 508 compliant markup.
Ext.override(Ext.form.TextArea, {
renderTpl: [
'<tpl if="label"><label for="{inputId}"><span>{label}</span></label></tpl>',
'<tpl if="fieldEl"><div>',
'<textarea id="{inputId}" type="{type}" name="{name}"',
'<tpl if="tabIndex">tabIndex="{tabIndex}" </tpl>',
'<tpl if="placeHolder">placeholder="{placeHolder}" </tpl>',
'<tpl if="style">style="{style}" </tpl>',
'<tpl if="maxRows != undefined">rows="{maxRows}" </tpl>',
'<tpl if="maxlength">maxlength="{maxlength}" </tpl>',
'<tpl if="autoComplete">autocomplete="{autoComplete}" </tpl>',
'<tpl if="autoCapitalize">autocapitalize="{autoCapitalize}" </tpl>',
'<tpl if="autoFocus">autofocus="{autoFocus}" </tpl>',
'></textarea>',
'<tpl if="useMask"><div></div></tpl>',
'</div></tpl>'
]
});