second of all

used as an adverb phrase, sometimes added after saying ‘‘first of all’’. thus the words ‘‘of all’’ are sometimes added to ‘‘second’’ in colloquial oral speech although it is generally considered either improper or, at best, unnecessary to do so in terms of grammar and logic, especially considering that it should be enough to use ‘‘of all’’ only once, that is to say after ‘‘first’’, and no matter how many elements are supposed to be listed.

adverb phrase used by way of emphasis, often to let someone know that one is not is a good mood, or has been offended by something.

one would be right in thinking that this adverb phrase is a way to make some particular matter sound more important than it actually is.

probably widely used in the entire english-speaking world, definitely quite of common usage in english canada.
example (taken from a show that is generally considered quite stupid, namely ‘‘love court’’, on much music, in canada):

man on a blind date in a limousine, on camera, talking to the woman sitting next to him

‘‘i got really drunk and hooked up with a fat chick once.

…

one of the four judges in a different place, played by (female) humorist dini dimakos
– first of all, you weren’t that drunk; and second of all, i was just bloated.’’

other example based on a context taken from real life:

young woman talking to a friend of hers while waiting for a city bus
‘‘so i told her, ‘hey, first of all, if bringing all those friggin’ goodies back home by six thirty in the evening yesterday really was so important, you should have said so right away. second of all, you knew perfectly well that i was unable to do it anyway since i didn’t have the car then’.’’