Probably from Middle Dutch jammeren cognate and reinforced by Middle English yeoumeren (“to mourn, complain”), from Old English ġeōmrian (“to lament”), from ġeōmor (“sorrowful”), from Proto-Germanic *jēmaraz (“miserable, sorrowful”), from Proto-Indo-European *yem- (“to hold, match, defeat”). Akin to German jammern.
- (intransitive) To complain peevishly.
- (intransitive) To talk loudly and persistently.
- (transitive) To repeat on and on, usually loudly or in complaint.
- (intransitive, rare) To make an outcry; to clamor.
- “yammer” in Douglas Harper, Online Etymology Dictionary (2001).
- “yammer” in Dictionary.com Unabridged, v1.0.1, Lexico Publishing Group, 2006.