Source

File: wp-includes/class-wp-term-query.php

protected function get_search_sql( $string ) {
		global $wpdb;

		$like = '%' . $wpdb->esc_like( $string ) . '%';

		return $wpdb->prepare( '((t.name LIKE %s) OR (t.slug LIKE %s))', $like, $like );
	}