from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. Something incredibly fast (now mainly used in comparison: like or faster than greased lightning).
From greased + lightning, believed due to the observation that greased machinery tends to run faster, and the notion that if a lightning strike (the fastest normally observed movement) could be greased, it might move even faster. Originally US usage but soon well known in UK due to Thackeray's use in 1848 (see cite). (Wiktionary)