Old English sped "success, prosperity, advancement," from Proto-Germanic *spodiz (cf. Old Saxon spod "success," Dutch spoed "haste, speed," Old High German spuot "success," Old Saxon spodian "to cause to succeed," Middle Dutch spoeden, Old High German spuoten "to haste"), from PIE *spo-ti- "speed," from *spe- "to thrive, prosper" (cf. Sanskrit sphayate "increases," Latin sperare "to hope," Old Church Slavonic spechu "endeavor," Lithuanian speju "to have leisure").
Meaning "quickness of motion or progress" emerged in late Old English (usually adverbially, in dative plural, e.g. spedum feran), emerging fully in early Middle English. Meaning "gear of a machine" is attested from 1866. Meaning "methamphetamine, or a related drug," first attested 1967, from its effect on users. Speed bump is 1975; figurative sense is 1990s. Full speed is recorded from late 14c. Speed reading first attested 1965. Speedball "mix of cocaine and morphine or heroin" is recorded from 1909.
