(The first D in this name is pronounced like 'th'in brother. The second D is pronounced like 'D' in 'dart'. The last s indicates plural number. )
Maahishaka or Maahishakas is the name of the people of the Maahishaka provinces ruled by the Maahishaka kings. This roughly corresponds to present Mysore state ie Karnaataka.
As was the custom in Samskritham, contry names are given by the people that inhabited it and the name is always in plural.
The king of a country derives his name by the country he ruled. E.g. Paanchaala is the ruler of the country Panchaalam,
Chaidya is the ruler of the country Chedi, Maagadha was the ruler of the country Magadha etc.
Maahishaka is clearly mentioned in Ashvamedha parva, along with Dravida and Aandhra which clearly indicate present Thamila Naadu and Aandhra Pradesh areas.
"After praying to Naaraayana, Nara, Sarasvathi and Vyaasa, then one should read the Jayam."
DEDICATED TO MY DEAR NIECE VYSHNAVI KRISHNA