I always thought that the SOS signs and telephones at the side of the road meant 'Someone's Stuck'! I think it makes a lot more sense than 'Save Our Souls'!
A childhood belief about road signs

others believed things like this
- I used to see "End Road Work" signs, and thought they were a sort of protest.— Sebastian
- I thought the lines in the sky left behind by airplanes were "sky scrapers". Makes sense.Anon
- I used to beleive that road signs grew out of the ground.— Tiana
- I used to believe that the sky had stop lights and road signs floating about for the airplanes.
— LoonaSM's - I thought a major general is more powerful than just a general (which still kind of makes sense to me)— Demond
- I thought the "To Let" signs on buildings meant they were public toilets.— Scottish Laddie