from
The Collaborative International Dictionary of English v.0.48
Knight service \Knight" serv"ice\Also Knight's service \Knight's
service\n.
1. (Feud. Law) The military service by rendering which a
knight held his lands.
2. (Eng. Feud. Law) A tenure of lands held by knights on
condition of performing military service. See {Chivalry},
n., 4.
[1913 Webster]
By far the greater part of England [in the 13th
century] is held of the king by knight's service. .
. . In order to understand this tenure we must form
the conception of a unit of military service. That
unit seems to be the service of one knight or fully
armed horseman (servitium unius militis) to be done
to the king in his army for forty days in the year,
if it be called for. . . . The limit of forty days
seems to have existed rather in theory than
practice. --Pollock &
Mait.
[Webster 1913 Suppl.]
3. Service such as a knight can or should render; hence, good
or valuable service.
[Webster 1913 Suppl.]