1915, adopted c.1952 as a scientific prefix meaning "one trillionth," from Sp. pico "a little over, a small balance," lit. "sharp point, beak," of Celtic origin (cf. Gaul. beccus "beak"). Picosecond first recorded 1966.
pref. [SI: a quantifier meaning * 10^-12] Smaller than nano-; used in the same rather loose connotative way as nano- and micro-. This usage is not yet common in the way nano- and micro- are, but should be instantly recognizable to any hacker. See also quantifiers, micro-.