autoship_frequency_label (filter)

(templates/cart/schedule-options.php) This filter allows devs to modify the label for the 'Schedule' label for the Frequency drop down menu for simple and variable products.

child-theme functions.php

function change_frequency_label($label, $product) {
    return 'How often?';
}
add_filter('autoship_frequency_label', 'change_frequency_label', 10, 2);