Definition of "knobber"

As soon as the knobber started galloping, all the other stags, who. till now, had taken but a languid interest, if any, in his movements, jumped on to their feet.

1906, Country life‎, volume 20, page 619

But even she was forced to confess that nothing was astir in the mossy wilderness. She climbed to the top of Craig Dhu and had a long spy, but, except for more hinds and one small knobber, living thing there was none.

1925, John Buchan, John Macnab, page 100

While I watched the young hind approached the knobber and, after standing by him for a moment, began to lick him

1968, Lea MacNally, Highland year

A mature stag chases a young male (a knobber) from the harem

1978 November 16, New Scientist, volume 80, number 1129, page 540

Harry chuckled. 'What is it, old son? Are you worried Natalie will go for a rummage in your undercarriage and come away empty-handed?'Ad spat Tango across the table, missing me by inches.'No, you knobber,' I said. “I'm meeting her parents for the first time tomorrow.'

2015, Ben Davis, The Private Blog of Joe Cowley: Return of the Geek, page 29