ETYM Old Eng. wo, wa, woo, AS. wâ, interj.; akin to Dutch wee, OS. and Old High Germ. wę, German weh, Icel. vei, Dan. vee, Swed. ve, Goth. wai; cf. Latin vae, Greek. Related to Wail.
Intense mournfulness; SYN. woefulness.

Used to express grief, regret, or distress.