ferret (v.)
early 15c., from ferret (n.), in reference to the use of half-tame ferrets to kill rats and flush rabbits from burrows; the extended sense of "search out, discover" is 1570s. Related: Ferreted; ferreting.
ferret (n.)
late 14c., from Old French furet, diminutive of fuiron "weasel, ferret," literally "thief," probably from Late Latin furionem (related to furonem "cat," also "robber"), from Latin fur (genitive furis) "thief."