An aglet or aiglet is a small plastic or metal sheath on the end of shoelaces (or any type of lace, though shoelaces are the most commonly referenced), which keeps the twine from unraveling and makes it easier to feed the lace through the eyelets.
The word "aglet" (or "aiglet") comes from Old French "aguillette" (or "aiguillette"), which is the diminutive of "aguille" (or "aiguilee"), meaning "needle". This in turn comes from "acus", the original Latin word for needle.
Aglets today are most often made of clear plastic, but in times past aglets were made of metal, glass, or stone. Many were highly ornamental, and made of precious metals such as silver. Before the invention of buttons, they were used on the ends of ribbons to fasten clothing together. Sometimes they would be formed into small figures. Shakespeare calls this type of figure an "aglet baby" in The Taming of the Shrew. (See aiguillette (ornament).) Purely decorative metal ornaments called aiguillette are sometimes features of modern military dress uniforms.