1610s, "to disperse," from see dis- + assemble. It seems to have become obsolete by 19c., and the main modern meaning "to take apart" (with intention to allow for re-assembly) is by 1893, probably a separate formation. Related: Disassembled; disassembling; disassembly.
disarm
disarmament
disarray
disarticulate
disarticulation
disassemble
disassociate
disassociation
disaster
disastrous
disavow