Tartan
The cloth that Scottish people wear for their kilts is called tartan. It is a patterned woolen fabric with colorful stripes and checks that is traditionally associated with Scottish culture and kilts.
Scottish
Tartan
Kilts
Kilts.
Yes, they originated in Scotland and are worn both by men and women.
They wore kilts and tarps.
They are known as kilts.
Most kilts are tartan so they are multi-coloured.
Kilts are Gaelic in origin, and Gaels populated both of those modern-day regions. So both of them have kilts, and they get them from the same place even if their styles have diverged over time. That said, the oldest records of them are from the Scottish Highlands.
They are all different patterns. Each different pattern used to represent the different Celtic clans, they still do but they don't tend to mean anything now and there are probably patterns that have nothing to do with any of the original clans.
The difference between kilts and skirts is largely cultural. Kilts are worn by men (Scottish usually) and made from heavy wool and cotton. Skirts worn by women and are made of a variety of materials.