Or mrowr {mer-ore'}; from marar; a bitter herb -- bitter(-ness).
see HEBREW marar
H4844. maror
[מָרֹר] noun masculine bitter thing, bitter herb (compare Late Hebrew id., bitter herb; on form see BaNB 194); — only plural מְרֹרִים Exodus 12:8; Numbers 9:11, מְרוֺרִים Lamentations 3:15; — bitter herbs, in Passover meal Exodus 12:8; Numbers 9:11 (both P); compare בַּמּ ׳הִשְׂבִּיעַנִי Lamentations 3:15, figurative of distress inflicted ("" לַעֲנָה).