late 15c.; see un- (1) "not" + breakable.

late 14c., originally in figurative sense of "unrestrained, ungoverned," from un- (1) "not" + bridled (see bridle (v.)). Similar formation in Middle Dutch ongebreidelt. Literal sense of "not fitted with a bridle" (of horses) is not recorded before 1550s. The verb unbridle (see un- (2)) is attested from c. 1400 in the literal sense; mid-15c. in the figurative sense.

1746, from un- (1) "not" + British.

c. 1300, in reference to vows or compacts, from un- (1) "not" + broken. Attested from late 15c. in reference to material things; 1510s in reference to courage, spirit, etc.; 1530s in reference to horses; 1560s in reference to the flow of time. Old English had ungebrocen.

late 14c., from un- (2) "reverse of" + buckle (v.1). Related: Unbuckled; unbuckling.

1530s, "to unload" (transitive), from un- (2) "reverse of" + burden (v.). Similar formation in German entbürden. Reflexive sense is recorded from 1580s. Related: Unburdened; unburdening.

Old English unbyrged "unburied," from un- (1) "not" + past participle of bury (v.).

early 14c., from un- (2) "opposite of" + button (v.). Related: Unbuttoned; unbuttoning.

c. 1400, "not summoned," from un- (1) "not" + past participle of call (v.). Similar formation in Swedish okallad, Danish ukaldet. With for and sense of "unnecessary, intrusive" it is first attested 1610.

1550s, from un- "not" + past-participle adjective from cancel (v.).