bond (n.)

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.

1670s, "to put in a bond" (transitive), from bond (n.). Intransitive sense "hold together from being bonded" is from 1836. Originally of things; of persons by 1969.

c. 1300, "in a state of a serf, unfree," from bond (n.) "tenant, farmer holding land under a lord in return for customary service; a married bond as head of a household" (mid-13c.). The Old English form was bonda, bunda "husbandman, householder," but the Middle English word probably is from Old Norse *bonda, a contraction of boande, buande "occupier and tiller of soil, peasant, husbandman," a noun from the past participle of bua, boa "to dwell" (from PIE root *bheue- "to be, exist, grow").

"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).