early 13c., "anything that binds, fastens, or confines," phonetic variant of band (n.1) and at first interchangeable with it. For vowel change, see long (adj.); also influenced by unrelated Old English bonda "householder," literally "dweller" (see bond (adj.)).
It preserves more distinctly than band the connection with bind and bound (adj.1) and is now the main or only form in the sense of "restraining or uniting force." From early 14c. as "an agreement or covenant;" from late 14c. as "a binding or uniting power or influence." Legalistic sense "an instrument binding one to pay a sum to another" first recorded 1590s. Meaning "a method of laying bricks in courses" is from 1670s. In chemistry, of atoms, by 1900.
"In the more despotic Norway and Denmark, bo'ndi became a word of contempt, denoting the common low people. ... In the Icelandic Commonwealth the word has a good sense, and is often used of the foremost men ...." [OED]. The sense of the noun deteriorated in English after the Conquest and the rise of the feudal system, from "free farmer" to "serf, slave" (c. 1300) and the word became associated with unrelated bond (n.) and bound (adj.1).
c. 1300, "legal condition of a serf or slave," from Middle English bond "a serf, tenant farmer," from Old English bonda "householder," from or cognate with Old Norse boandi "free-born farmer," noun use of present participle of boa "dwell, prepare, inhabit," from PIE *bhow-, from root *bheue- "to be, exist, grow." For sense evolution, see bond (adj.). The sexual sado-masochism sense is recorded by 1963 (in a New York law against publications portraying it).
It forms all or part of: band; bandanna; bend; bind; bindle; bond; bund; bundle; cummerbund; ribbon; woodbine.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit badhnati "binds," bandhah "a tying, bandage;" Old Persian bandaka- "subject;" Lithuanian bendras "partner;" Middle Irish bainna "bracelet;" Old English bendan "to bend a bow, confine with a string," bindan "to bind," Gothic bandi "that which binds."
Meaning "curve or make crooked" (early 14c.) is via the notion of bending a bow to string it. Intransitive sense of "become curved or crooked" is from late 14c., that of "incline, turn from the straight line" is from 1510s. Figurative meaning "bow, be submissive" is from c. 1400. Cognate with band, bind, bond, and Bund. Related: Bended; bent; bending.