functions.php

<?php


add_filter( 'facetwp_i18n', function( $string ) {
    if ( isset( FWP()->facet->http_params['lang'] ) ) {
        $lang = FWP()->facet->http_params['lang'];

        $translations = array();
        $translations['cn']['Select'] = 'The Chinese translation for Select';

        if ( isset( $translations[ $lang ][ $string ] ) ) {
            return $translations[ $lang ][ $string ];
        }
    }

    return $string;
});