The word G. {ambos >>} ammos “byrne, hauberk, cuirass” (types of upper-body armor) appeared in the Gnomish Lexicon of the 1910s as an elaboration of am “breast, front (chest)” (GL/19). This word was also an element in a number of words for “robin” or “red-breast”: G. ammogrint (GL/19), G. crinthammos (GL/27) and G. amosgarn (PE13/110), the last of these appearing Gnomish Lexicon Slips modifying that document.

Conceptual Development: ᴱN. am(b)os “breastplate” appeared in Early Noldorin Word-lists of the 1920s as an elaboration of ᴱN. am(b) “breast”, but both these words were deleted (PE13/137).

Neo-Sindarin: For purposes of Neo-Sindarin, I would adapt this word as ᴺS. ammos “breast, chest” rather than “breastplate”; it seems clear that ammos could also mean “breast, chest” based on its use in Gnomish “robin” = “red-breast” words. It might be an ancient combination of √AM “up” and ᴹ√OS “around”, perhaps with the original sense “upper enclosure (of the body)”.