small device made to connect to a computer, now especially for use of wireless broadband or protected software, by 1982, perhaps 1980, perhaps suggested by dangle and dong (n.).
Entries linking to dongle
dangle v.
1590s, intransitive, "hang loosely, be suspended so as to sway in the wind," probably from Scandinavian (compare Danish dangle, Swedish dangla "to swing about," Norwegian dangla), perhaps via North Frisian dangeln. Transitive sense of "carry suspended so as to swing or sway" is from 1610s. Related: Dangled; dangling.
dong n.
"penis," 1891, slang, of unknown origin. Perhaps suggested by dingus and other names for unnameable things; perhaps suggesting of a sound of striking (clapper of a bell?); perhaps there's an element of donkey in it.