Getting parent category and showing it through wordpress shortcode paste this code in functions.php

parent_terms.php

/**
	* Create [parent_category] shortcode
  * Shortcode can have this attribute
  * taxonomy //string
	 */
add_shortcode( 'parent_category', 'get_parent_category' );
function get_parent_category( $atts ) {
	$arg = shortcode_atts( array(
		'taxonomy' => 'category', //default taxonomy
	), $atts );
	$post_cats = get_the_terms( get_the_ID(), $arg['taxonomy'] );
	$cats_list = array();

	foreach( $post_cats as $post_cat ) {
		if( $post_cat->parent == 0 ) {
			$cats_list[] =  $post_cat->name;
		}
	}
	$cats_html = join( ", ", $cats_list );
	return $cats_html;
}