Origins unknown; used as a
codeword to describe people hooking up; now used as common slang in (mostly the north of) Scotland to describe any kind of sexual activity, and indeed many other activities which have little
or nothing to do with sex, and is generally used to indicate that something fortunate has occurred. It can be used as a legitimate verb in regular conversation, but it is normally just shouted, and is accompanied by a hand action where one puts the thumb and middle finger together, and taps them with
the index finger.