The earliest word for “food” in precursors to the Sindarin language was G. môs “food (of men)” (GL/56, 58), probably based on the early root ᴱ√M(B)ASA “cook, bake” (QL/59). This became ᴱN. math “food” in Early Noldorin Word-lists of the 1920s, appearing only in its lenited form vath as an element in ᴱN. orvath “foodless” (PE13/155). In The Etymologies of the 1930s Tolkien had N. mann “food” as a derivative of primitive ᴹ✶matna under the root ᴹ√MAT “eat”, but the version of the entry where this form appeared was struck out (EtyAC/MAT). The primitive form ✶matnā “food” did reappear in the early 1950s, however (PE22/136).
Neo-Sindarin: Of the above, I prefer ᴺS. math for “food”. I first saw math proposed as the Neo-Sindarin word for “food” in a list of neologisms by Elaran on the Vinyë Lambengolmor Discord Server (VLDS) from 2018. I prefer math because I tend to assume Q. matta is derived from ✱mattā rather than ✶matnā to avoid certain phonological difficulties; see that entry for discussion. If you are not concerned with those difficulties, ᴺS. mann “food” is also viable.
The earliest word for “food” in precursors to the Sindarin language was G. môs “food (of men)” (GL/56, 58), probably based on the early root ᴱ√M(B)ASA “cook, bake” (QL/59). This became ᴱN. math “food” in Early Noldorin Word-lists of the 1920s, appearing only in its lenited form vath as an element in ᴱN. orvath “foodless” (PE13/155). In The Etymologies of the 1930s Tolkien had N. mann “food” as a derivative of primitive ᴹ✶matna under the root ᴹ√MAT “eat”, but the version of the entry where this form appeared was struck out (EtyAC/MAT). The primitive form ✶matnā “food” did reappear in the early 1950s, however (PE22/136).
Neo-Sindarin: Of the above, I prefer ᴺS. math for “food”. I first saw math proposed as the Neo-Sindarin word for “food” in a list of neologisms by Elaran on the Vinyë Lambengolmor Discord Server (VLDS) from 2018. I prefer math because I tend to assume Q. matta is derived from ✱mattā rather than ✶matnā to avoid certain phonological difficulties; see that entry for discussion. If you are not concerned with those difficulties, ᴺS. mann “food” is also viable.