The word alack popped up in a book I'm reading (The Historian I think, though it could have been in The Blue Girl) and it seemed like a good word to feature. The phrase "alas and alack" comes to mind, but in the novel, alack was used on its own.
Alack is used to express sorrow, regret, or alarm
The OED adds:
Especially in phrases alack the day! alack-a-day! originally ‘Shame or reproach to the day! Woe worth the day!’ but in later usage of mere surprise, and aphetized* lack-a-day!* aphetize, another good word. A linguistic term: having undergone aphesis (the removal of an unstressed initial vowel).