woocommerce_out_of_stock_message filter-hook . WC 1.0

Usage

add_filter( 'woocommerce_out_of_stock_message', 'filter_function_name_5052' );
function filter_function_name_5052( $__ ){
	// filter...

	return $__;
}

$__

-

Where the hook is called

<p class="stock out-of-stock"><?php echo esc_html( apply_filters( 'woocommerce_out_of_stock_message', __( 'This product is currently out of stock and unavailable.', 'woocommerce' ) ) ); ?></p>

Where in WP core the hook is used WooCommerce