BELDAM (like "belsire," grandfather, from the Fr. bel, good, expressing relationship; cf. the Fr. belle-mère, mother-in-law, and dame, in Eng. form "dam," mother), strictly a grandmother or remote ancestress, and so an old woman; generally used contemptuously as meaning an old hag.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)