'Harping on' is still in common usage: I often hear it and use it myself occasionally, interchangeable with 'rabbiting on', 'waffling on' and others.
My late grandma liked her minced oaths and euphemisms, including 'by Jove', 'Gordon Bennett', 'good grief' and 'daft ha'p'orth'. My grandad still says 'I'm going to pay a call' as a euphemism for going to the toilet.
My late grandma liked her minced oaths and euphemisms, including 'by Jove', 'Gordon Bennett', 'good grief' and 'daft ha'p'orth'. My grandad still says 'I'm going to pay a call' as a euphemism for going to the toilet.