Thankyou Rowan. I wouldn't have found myself that far back.

Rhyme refused is how I describe them. Usually adding the word "telegraphed" to show that it is expected.

By making it obvious and refusing the rhyme you get humour from it. Particularly if you can use aliteration with the "refused" word, and drag-out the humour.

I use the device sometimes in my songs.

Another trick is to refuse the rhyme in it's expected place and then place it internally to another line and end the line with the same rhyme. If it makes the words stand out it has done its job, humour or serious.