I was on board the Cutty Sark yesterday and I think the idiom dates from that time (1880s)
Ships that were sailing abroad would offer delivery of items for wait. That meant that it was a one-off thing and they would deliver it - much later - at the required harbour, for someone to pick up
I believe Walt is the name of the man who died. The girl presumably asked Walt's son for information about Walt, and the son is going to give the girl a lot of details, perhaps sordid, about Walt and his life.