From Mrariy; a Merarite (collectively), or decendants of Merari -- Merarites.
see HEBREW Mrariy
H4848. Merari
II. מְרָרִי adjective, of a people of above, only with article as substantive collective ׳הַמּ Numbers 26:57.
II. מרר (√ of following; perhaps (so Thes) compare Arabic pass by, go, sometimes flow, cause to flow, water-course).