Precaution, n.
Etymology: [F. précation, L. praecautio, fr. praecavere, praecautum, to guard against beforehand; prae before + cavere be on one's guard. See Pre-, and Caution.]
1. Previous caution or care; caution previously employed to prevent mischief or secure good; as, his life was saved by precaution. They [ancient philosophers] treasured up their supposed discoveries with miserable precaution. J. H. Newman.
2. A measure taken beforehand to ward off evil or secure good or success; a precautionary act; as, to take precautions against accident.
1 other Webster entry under this spelling
Precaution, v. t.
1. To warn or caution beforehand. Locke.
2. To take precaution against. [R.] Dryden.
Shades of meaning
Fernald has no entry of its own for precaution; he lists it under care.
Where he writes about it:
Precaution is allied with care, prudence with caution; a man rides a dangerous horse with care; caution will keep him from mounting the horse; precaution looks to the saddle-girths, bit and bridle, and all that may make the rider secure. — from care