"Pico" is the
Spanish and
Portuguese word for
peak -- the pointed top of a
mountain. Because of this, there are many mountains named Pico this or Pico that, and sometimes just plain Pico. (Particularly in Spanish speaking countries).
There is also an island called Pico (in Portugeuse Ilha do Pico), in the north Atlantic. It is the second largest of the Azores (433 sq. km. {168 sq. mi.}). It's named after it's mountain, Pico Alto (high peak), which also happens to be a volcano. Pico Alto is the highest point in Portugal (2,351 m).
Pico can also be translated as beak (of a bird), pick (noun, not verb), pickax, or 'a little bit'. Due to this it is also used as an amusing reference to males' private parts (a mountain? a spike? a little bit? The wordplay is endless).
Besides meaning one trillionth (10-12), the prefix pico- also refers to other really, really small things (For example, picornavirus).