from that Wiki link:
>> The term “cracker” is derived from the Gaelic “craic”, meaning entertaining conversation or boasting
There was a Van Morrison song about 20 yrs ago where he does a bit of talking and says, “...and the crack (craic) was good...” in that sense.
Coney Island
Coming down from Downpatrick
Stopping off at St. John’s Point
Out all day birdwatching
And the craic was good
http://www.lyricsaholic.com/van-morrison-coney-island-lyrics.html