sudden (adj.)

late 13c., sodein, sodaine, of actions, events, conditions, "unexpected, unforeseen;" also "happening all at once and without notice;" from Anglo-French sudein, sodein or directly from Old French sodain, subdain "immediate, sudden" (Modern French soudain). This is from Vulgar Latin *subitanus, a variant of Latin subitaneus "sudden," from subitus past participle of subire "go under; occur secretly, come or go up stealthily," from sub "up to" (see sub-) + ire "come, go" (from PIE root *ei- "to go").

The present spelling was not finally established till after 1700; by far the commonest spelling in the 1st folio of Shakes. is sodaine, and suddain lasted on into the 1st quarter of the 18th c. [OED].

The noun meaning "that which is sudden, a sudden need or emergency" is attested by 1550s, from the adjective, but is obsolete save for all of a sudden "sooner than expected," a phrase attested by 1680s (earlier of a sudayn, 1590s; upon the soden, 1550s).

Sudden death is from c. 1400 in a literal sense, "summary death." In sports, with reference to tie-breakers, it is attested by 1927, probably from earlier use in reference to coin tosses (1834), as opposed to two-out-of-three, etc. Related: Suddenness.