1620s, "power to make use of, right to dispose of or control;" see dispose + -al (2). Meaning "a disposing" (of a daughter by marriage, of money by a will, of an estate by sale, etc.) is from 1650s; of waste material, from c. 1960, originally in medical use.
used all the resources at his disposal
display
displease
displeasure
disport
disposable
disposal
dispose
disposed
disposition
dispossess
dispossession