'Ne'er cast a clout till May be out' refers to not taking off your winter vest until the may blossom flowers ('may' being another name for hawthorn - the small white flowers you see in hedges in late spring).
I love the origins of old sayings.
'Above board' (meaning honest) is thought to refer back to the middle-ages when a 'dining table' was simply a board resting on the diners' knees - an honest man kept his hands above the board.
'Turning the tables' is from a similar time, but in richer houses the table was a board placed on trestles - one side of the board was for everyday use, and was rough and damaged through use; the other side was smooth and only used for 'best' and to impress guests - 'turning the tables' and 'taking the rough with the smooth' both come from this practice.
'Worth his salt' dates to a time when salt was very valuable and people were paid in salt (literally, a 'salary') - so a man who worked hard was 'worth his salt'.
Back to the orginal post - my grandma used to say 'billy-doo' (pronounced that way) to mean a short note. It's no doubt a corruption of billet-deux.
A favourite weather saying in our family was always "it's a bit black over by Will's mother's" if there was a dark cloud looming! My grandma always used to say there was promise of the weather clearing up if there was enough blue sky to make a sailor a pair of trousers!
