During the days of the windjammers, a ship had hundreds of ropes. If the ends unraveled, you'd be headed for a tangled mess. So, when work was slack, the captain would order sailors to tape or whip the loose (unraveled) ends. A man with nothing else to do was "at loose ends." If we are at loose ends today, we also confront spare time - or unresolved matters.
Wooden sailing vessels were especially vulnerable to high winds. If a mast snapped, sailors would lash a pole in place called a "jury mast" to serve until a new mast could be fitted in port. This makeshift mast (it is defined in the "Seaman's Grammar" of 1627) was notable for its short-term usage - a day or two. The French word "jour" (day) became "jury" and "jerry." Landsmen adopted the term to mean any flimsy but temporary construction.
It wasn't until the 17th century that this word came to mean the horns or sensory organs of an insect. A century later, Charles Darwin used the term to refer to the long, slender parts of some orchids. The original sense, however, derived from the long, tapered horizontal arms from which sails were hung on sailing vessels of old. The modern meaning, as in radio and television aerials, came into use in 1902.
Once, only pirates cruised
In the 17th century, a "cruise" would not make you feel at ease. Back then, freebooters preyed on treasure ships. The predator did not sail on a straight course but would cross and recross shipping lanes, looking for targets. This zigzag sailing was called "kruisen" from the Dutch "to cross." English sailors borrowed the term and called it "cruise." Pleasure-boaters later absconded with the term.
From Elizabethan times through the 1800s, British warships were classified by the number and weight of their guns. Six rates were applied to the vessels, and first-rate was the highest. Before long, the word "rate" was used generally to define the level of quality.