One of the joys of researching word origins and usage is discovering facts such as that the five English words formed on the frame of b_nd, with different vowels, are cognates, all stemming from a common proto-Indo-European ancestral verb meaning “restrain.”
Band, meaning “a flat strip” or “something that binds,” came to refer not only to an object with either or both of those characteristics but also to an organized group of people, perhaps from the use of uniform pieces of cloth worn by affiliated warriors. This usage extended to refer to a group of musicians attached to a military unit, from which derived the use of the word for a civilian ensemble. Band is also a verb, meaning “bind” or “fasten” in one sense or “join” in another.
Bend began as a verb describing fettering, or restraining of a person’s or animal’s feet, and the similar action of stringing a bow; from there it came to refer to any turning of a straight line or object and, as a noun, to a physical turn.
To bind originally meant to tie something or someone up, as if to fasten or restrain, or to dress a wound, and later acquired the figurative meaning of “commit,” “oblige,” or “require.” The noun bind usually applies to the figurative sense, often with the connotation of being placed in an awkward situation, although someone may place someone else in a physical bind, as in wrestling.
Bond, meanwhile, developed as a variant of band and describes physical adhesions, forces, and restraints as well as financial or legal documents, plus figurative connections, such as that described in the phrase “bonds of matrimony.” Like the related words above, it has a verb form as well.
The last and least common word in this family is bund, taken directly from the German word for a confederacy or league, used in English to refer to a political organization, especially one for German-Americans, such as a pro-Nazi group that flourished before World War II. There is no verb form for this word. Also, the word describes a type of levee-type embankment often used in Asia; this term, ultimately from Persian, may be distantly related to the other terms.