- (archaic) Please explain (something the requester does not yet understand).
- Pray tell us, how will they fare while you are away?
- (idiomatic, usually sarcastic) Expressing incredulity, please explain (some claim or position the speaker doubts).
- But how, pray tell, do you "notice" something that happens when you're asleep?
When "pray" was used to emphasize requests, this standard construction (as, "pray come here", "pray help us", "pray leave me") was an earnest request for information. The phrase is now, however, usually used ironically to emphasize the unacceptability of something, especially when highlighting a logical fallacy.