|Definition - The practice of using metronymics, names derived from either your mother's name or the names of one of your maternal ancestors.|
Etymology - The word derives from the Greek metros, mother + onoma, name.
Oxford English Dictionary - Its first citation is from 1891:
"M. Reclus finds what he calls ‘metronymy’ in Egypt under the Ptolemies. ‘The newly married man even dropped his own name to take that of his wife’."
(Sat. Rev. 31 Jan. 140/1 )