leash (v.) Look up leash at Dictionary.com
"to attach to or with a leash," 1590s, from leash (n.). Related: Leashed; leashing.
leash (n.) Look up leash at Dictionary.com
"thong for holding a dog or hound," c. 1300, from Old French laisse "hound's leash," from laissier "loosen," from Latin laxare, from laxus "loose" (see lax). The notion seems to be of a string loosely held. Figurative sense attested from early 15c. The meaning "a set of three" is from early 14c., originally in sporting language.