Why are Yorkshiremen called Tykes?

Cem up in conversation at work t'other day. Why dost tha' call thi'sen Tykes someone asked mi. Eeh, lad, ah'll not mind confessing that am bahrt knowledge on such a reason ah said to 'im.

I can't find it on the net.
Does anyone else know why us Yorkshire men are called Tykes?

'According to Dr Arnold Kellett' s book 'The Yorkshire Dictionary', a tyke is another word for a dog or cur (from Old Norse tika, meaning bitch), especially a small mongrel terrier used for catching rats etc. From the common sight of a Yorkshireman owning such a dog, the nickname was commonly applied to anyone born and bred here. Arnold is a regular contributor to Dalesman Magazine.'

'Tyke' is well known throughout much of the UK as a word for a dog. I certainly knew it in the East End of London. So, perhaps, not just Yorkshire? Origin is interesting - thanks.