Where Did Kilo, Mega, Giga and All Those Other Prefixes Come From?

They have entered our language. Everyone uses them. The terms, particularly with "byte", are almost commonplace. Kilobyte, Megabyte and Gigabyte are part of our lexicon.

But do you know where they came from?

First, let's show the terms:

Kilo	10001	103	1,000
Mega	10002	106	1,000,000
Giga	10003	109	1,000,000,000
Tera	10004	1012	1,000,000,000,000
Peta	10005	1015	1,000,000,000,000,000
Exa	10006	1018	1,000,000,000,000,000,000
Zetta	10007	1021	1,000,000,000,000,000,000,000
Yotta	10008	1024	1,000,000,000,000,000,000,000,000

 

Ok. So where did they come from?

Kilo comes from the Greek khiloi and means, curiously enough, 1000. It is interesting enough, the only prefix with a direct numerical meaning.

The next three come from Greek and Latin and are either descriptive or mythological.

Mega comes from the Greek mega meaning "great", as in "Alexandros O Megas" or "Megas Alexandros" (Alexander the Great).

Giga comes from Latin gigas meaning "giant".

Tera comes from Greek teras meaning "monster".

Now we return to numbers. Though not direct numerical references, the next two are indirect references.

Peta comes from the Greek pente meaning five. This is the fifth prefix (for 1000⁵). This term, and the next one, were both added in 1975 by the General Conference of Weights and Measures (abbreviated CGMP because it is in France)

Exa comes from Greek hex meaning six. This is the sixth prefix (for 1000⁶). Taking "Hexa" and making the "H" silent (as it is in France, home of  the CGMP) gives "Exa".

Here we leave the numerical references again. Unable to return to the mythological (after great, giants and monsters what else is there), we move to the Latin alphabet. For reasons I don't know, we start with the last letter (Zetta), working backwards to the beginning.

Zetta, often mistaken for the Greek Zeta, is the last letter of the Latin alphabet. This prefix and the next one were added in 1990 by CGMP.

Yotta is the penultimate (next to last) letter of the Latin alphabet.