Rename Post Formats In WordPress https://wp.me/p1lTu0-h6Q

functions.php

add_filter( 'gettext_with_context', 'rename_post_formats', 10, 4 );

function rename_post_formats( $translation, $text, $context, $domain ) {

    $names = array(
        'Audio'  => 'Custom Name',
        'Chat' => 'Custom Name',
        'Aside' => 'Custom Name',
    );
    
    if ( $context == 'Post format' ) {
        $translation = str_replace( array_keys( $names ), array_values( $names ), $text );
    }
    
    return $translation;
}