Good info, Guest. Still doesn't speak to the issue of whether the phrase evolved from "let us smile be' your umbrella" or whether that phrase was known in an earlier poem or song.

Wish I were better at searching literary archives so I could delve more into the history of the phrase. I've no doubt that by 1925 in the US nobody used the contraction "be'" for "beneath." My understanding was that that usage was older English and probably from the other side of the pond.

Genie