The initial idioms of the letter O

once	once (the) word gets out
Once a priest, always a priest	once again
once and again	once and for all
Once bitten, twice shy	once hell freezes over
once in a blue moon	once in a lifetime
once in a while	once more
once or twice	once over lightly
once the dust has settled	once upon a time
once you go black, you never go back	once-in-a-lifetime chance
once-over	once-over-lightly
one’s bag	one’s ball and chain
one’s best shot	one’s better half
one’s bottom dollar	one after another
one after the other	one age with (someone)
one and all	one and one