The Collaborative International Dictionary
Agistor
Agister \A*gist"er\, Agistor \A*gist"or\, n. [Anglo-Norman agistour.] (Law)
Formerly, an officer of the king's forest, who had the care of cattle agisted, and collected the money for the same; -- hence called gisttaker, which in England is corrupted into guest-taker.
Now, one who agists or takes in cattle to pasture at a certain rate; a pasturer.
--Mozley & W.
Wiktionary
agistor
n. 1 One who agists or takes in cattle to pasture at a certain rate; a pasturer. 2 Formerly, an officer of the king's forest, who had the care of cattle agisted, and collected the money for the same; hence called gisttaker, which in England is corrupted into guest-taker.