Not all Irish Travellers were tinkers (from tinsmithing or tinsmith) as there were horse dealers, market traders etc.
Irish Travellers have their own distinct culture, traditions, way of life and language and are indigenious to Ireland and are said to be here in Ireland before the Celts arrived in Ireland 500 yrs BC.
"No, its a term, often negative"
verb--To engage in minor repairs or inventing.
John's always tinkering. His latest widget gets my mail and throws away the ads.
Another meaning of tinkers is esctasy pills.