Kurukshetra is named after king Kuru, after which the dynasty was called Kuru Vansh.
He was son of King Samvaran and Tapti. Tapti was daughter of Suryadev. Samvaran had to perform great penance to please Suryadev and pass his test before Suryadev allowed the marriage.
Kuru ploughed the field of Kurukshetra for many years and won a boon from Indradev that, whoever dies in that field either due to hunger or in battle will go to heaven.
Krishna and Bhishma Pitamah were aware of this boon, hence they selected the ground of Kurukshetra as battlefield of Mahabharat.