I liked the analysis from Disappearing Idioms. It described a “wet blanket as “…a person, although sometimes it can be a thing…that be counted on to spoil the fun or dampen the enjoyment of others.” What really attracted me was the “Three Famous Wet Blankets.” The first was the Eeyore donkey from Winnie-the-Pooh, Sad Sack from Yank Magazine, and my favorite, Joe Btfsplk of Lil’ Abner who “…travelled with his own black cloud overhead.” The explanation of the origin is that it refers to 1660 references to keeping a thoroughly wetted blanket handy to smother a flare-up in confined spaces.