autoship_frequency_cart_order_item_schedule_display_label
Can be used to customize the "Schedule" label found on a Scheduled Order's metadata and in the Cart items metadata displayed.
Example
// customize item label 'Schedule' to 'Subscribe' in cart function xx_change_so_freq_display_label ($label){ return 'Subscribe'; } add_filter('autoship_frequency_cart_order_item_schedule_display_label', 'xx_change_so_freq_display_label', 10, 1);