From the name of Mount Monadnock in New England, which derives from an Abenaki word, perhaps menonadenak, menonadenek (“smooth mountain") or menadenak, menadenek (“isolated mountain"), from aden (“mountain").
English Wiktionary. Available under CC-BY-SA license.
Monadnock (in New Hampshire, nearN.E.Massachusetts), the Blue Hills near Boston, Greylock, in the north-west, and Wachusett in the centre, are the most commanding remnant-summits (known generically as " Monadnocks ") of the original mountain system.
South of the mountains a plateau-like surface - a part of the New England Uplands - broken by residual mountains, or " monadnocks " (a term derived from Mount Monadnock, 3186 ft.
Extending from Mount Monadnock in Cheshire, the S.W.
The type of this class of forms is Mt Monadnock in south-western New Hampshire, a fine example of an isolated residual mass rising from an upland some 1500 ft.
This knob or ridge may be appropriately regarded as an ancient physiographic fossil, inasmuch as, being a monadnock of very remote origin, it has long been preserved from the destructive attack of the weather by burial under sea-floor deposits, and recently laid bare, like ordinary organic fossils of much smaller size, by the removal of part of its cover by normal erosion.