The initial idioms of the letter O

oinker	ointment
OJ	OJ someone
okay	okey-dokey
OL	the old Adam
old as Adam	old as Methuselah
old as the hills	old battle-axe
old chestnut	old college try
old college try, the	the old days
old enough to be mother	old enough to vote
old flame	old fogey
old girl	Old habits die hard
old hand	old hand at something
old hat	old heave-ho
in and out	old lady
the Old Lady of Threadneedle Street	old maid