What’s the difference between a bond and a bound, and the relationships of the verb and adjective forms? Both words have to do with constraints, but the multiple meanings aren’t necessarily related.
A bond is something that binds — literally, as with chains, or figuratively, as an agreement or a financial obligation — and the word is etymologically related to bind as well as band. The last word is from Old Norse and is related to the Scandinavian word bindan, which means “to bind.” Borrowed into English, that word developed into two terms: band, meaning “something that binds,” and bande, meaning “a flat strip.” With the loss of the appendage e, the four-letter word now represents both meanings.
The latter sense of band is the origin of the use of the word in “rubber band” as well as the reference to a musical ensemble (from the military origin of the band, whose members, as soldiers, would wear insignia, originally in the form of strips of cloth, in common) and, by extension, any group that travels together or associates.
However, the second syllable of husband, which means “dweller,” is etymologically unrelated to band. (The first element, as you may have guessed, means “house.”) Nevertheless, it became associated with bond because although the Old English word bonda means “householder,” in the feudal era, the connotation was of a serf or a tenant farmer, hence the idea of restraint.
A bound is a limit, and the verb form means “to form the boundary of,” but from the sense of bind, it also means “fastened” or “compelled.” The adjective bound means “confined” (“I’m bound to my desk for the next eight hours”) or “obligated” (“I’m bound to honor my agreement”), as well as “sure” (“It’s bound to get better”) or “determined” (“She is bound to get her way”). Note, however, that this last sense can seem ambiguous: “She is bound to get her way” could be construed as referring to certainty, not resolve.
The same word seen in such constructions as “I’m bound for Europe” and in the compound homebound is unrelated; that word comes from a sense of “to prepare,” another meaning for the word that formed the second part of husband. The bound used, for example, in the sentence “They watched him bound from group to group” or forming the root of rebound is from a third source, a French word meaning “leap” or “echo.”
The noun and verb bend, by the way, is related to band and bind, as well as to the German word bund, meaning “league.”