Old English unbindan, "to free from binding," from un- (2) "opposite of, reverse" + bind (v.). Similar formation in Old Frisian unbinda, German entbinden, Dutch ontbinden. Literal and figurative senses both present in Old English.
Suæ huæt ðu unbindes ofer eorðu bið unbunden in heofnum. [Lindisfarne Gospels, Matthew xvi.19]
Unbound is from Old English unbunden, in literal sense. Figurative sense first attested late 14c.; of books from 1540s.
"fastened," mid-14c. in figurative sense of "compelled," earlier in fuller form bounden (c. 1300), past-participle adjective from bind (v.). Meaning "under obligation" is from late 15c.; the literal sense "made fast by tying (with fetters, chains, etc.)" is by 1550s. In philology, designating a grammatical element which occurs only in combination with others (opposed to free), from 1926. Smyth has man-bound (1867), of a ship, "detained in port for want of a proper complement of men."
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.
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.