different between inconstancy vs inconsideration

English

in- +? constancy or inconstant +? -cy

inconstancy (countable and uncountable, plural inconstancies)

From Middle French inconsideration and its source, Latin inconsider?ti?nem.

inconsideration (countable and uncountable, plural inconsiderations)

Lack of due consideration; inattention to consequences, thoughtlessness.
- , II.11:
  new trained Souldiers, and such as are but novices in the trade, doe often headlong, and hand over head cast themselves into dangers, with more inconsideration, than afterward when they have seene and endured the first shocke, and are better trained in the schoole of perils.

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