- A stem-winding watch.
- A rousing oration, especially a political one.
Note contradictory senses of “rousing speech” (earlier sense) and “boring speech” (later sense); use in the latter sense may be proscribed as a corruption, and is a folk etymology.
US, mid-late 19th century, originally referring to then-recent stem-wind watches (invented in 1840s, commercialized initially 1850s by Patek Philippe & Co.). These were expensive, top-notch watches, hence generalized (1892 ) to “top-notch”, particularly applied to speeches, or to the orator in question. Non-speech senses later fell out of use. Nuance of “rousing” speech possibly by analogy with watch being wound up (“tighten by winding, excite, rouse”).
Circa 2000, later sense of “interminable speech” a folk etymology, in sense “a speech that lasts so long one must wind one’s watch”.