From The Collaborative International Dictionary of English v.0.48:
Quarantine \Quar`an*tine"\, v. t. [imp. & p. p. Quarantined;
p. pr. & vb. n. Quarantining.]
To compel to remain at a distance, or in a given place,
without intercourse, when suspected of having contagious
disease; to put under, or in, quarantine.
[1913 Webster]
From The Collaborative International Dictionary of English v.0.48:
Quarantine \Quar"an*tine\, n. [F. quarantaine, OF. quaranteine,
fr. F. quarante forty, L. quadraginta, akin to quattuor four,
and E. four: cf. It. quarantina, quarentine. See Four, and
cf. Quadragesima.]
1. A space of forty days; -- used of Lent.
[1913 Webster]
2. Specifically, the term, originally of forty days, during
which a ship arriving in port, and suspected of being
infected a malignant contagious disease, is obliged to
forbear all intercourse with the shore; hence, such
restraint or inhibition of intercourse; also, the place
where infected or prohibited vessels are stationed.
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Note: Quarantine is now applied also to any forced stoppage
of travel or communication on account of malignant
contagious disease, on land as well as by sea.
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3. (Eng. Law) The period of forty days during which the widow
had the privilege of remaining in the mansion house of
which her husband died seized.
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Quarantine flag, a yellow flag hoisted at the fore of a
vessel or hung from a building, to give warning of an
infectious disease; -- called also the yellow jack, and
yellow flag.
[1913 Webster]