I'm wondering if there is a word that means to 'multiply by ten'.
I'm curious based on my interest in the word decimate, which used to mean to remove a tenth of something.
That word is decuple (Collins Dictionary):
(transitive) to increase by ten times
It can also be used as a noun or adjective.
I think that the word you may be looking for could be tenfold. According to Collins (http://www.collinsdictionary.com/dictionary/english/tenfold):
equal to or having 10 times as many or as much ⇒ "a tenfold increase in population"
composed of 10 parts
- by or up to 10 times as many or as much ⇒ "the population increased tenfold"
Regarding the etimology, according to Etymonline (http://www.etymonline.com/index.php?term=tenfold):
tenfold (adj.) Old English tienfeald; see ten + -fold. As an adverb in modern use from 1530s.
And also from Etymonline (http://www.etymonline.com/index.php?term=-fold&allowed_in_frame=0):
-fold Multiplicative word-forming element attached to numerals, from Old English -feald, Northumbrian -fald, from Proto-Germanic *-falthaz (cognates: Old Saxon -fald, Old Frisian -fald, Old Norse -faldr, Dutch -voud, German -falt, Gothic falþs), comb. form of *falthan, from PIE *polt-, extended form of root *pel- (3) "to fold" (cognates: Greek -paltos, -plos; Latin -plus; see fold (v.)). Native words with it have been crowded out by Latinate double, triple, etc., but it persists in manifold, hundredfold, etc.
Some examples of use:
"The annual crop of wheat in the regency, is estimated at 7,200,000 bushels and with the proper cultivation might be tenfolded"
From "A compendious and complete system of modern geography: or, A view of the world" by Jeddediah Morse (1812)
Another example of use:
"It is nice to dream about tenfolding one's money in a year and a half"
From "The Zurich Axioms" by Max Gunther (2005)
In plain English, if you multiply something by 10, you have increased its order of magnitude by one.
More technically, when using the base 10 number system, all numbers can be written in exponential form, such as 1.984 x 103, and if you multiply by ten you merely increment the exponent by one: 1.984 x 104. Therefore, the order of magnitude is dependent on your base and on whether your scale is linear, logarithmic, or something else.
Decimate is currently shifting its meaning. The original sense of the word was to kill 10% of a group of people. Mercifully, that practice was almost completely abandoned 2000 years ago. Therefore, most people use the word to mean "great destruction."
In plain English, to divide something by ten is to decrease it by an order of magnitude.
The single word meaning "multiply by ten" is decuple (it's like "triple" or "quadruple", but much rarer).
intr. & tr.v To multiply or be multiplied by ten.
[Middle English, from Old French, from Late Latin decuplus : Latin decem, ten; see dekm̥ in the Appendix of Indo-European roots + Latin -plus, -fold; see pel-2 in the Appendix of Indo-European roots.]
(American Heritage Dictionary)
As noted in the commments beneath Jimi Oke's answer, this word has various pronunciations:
I wrote an answer about the pronunciation of "tuple" that explains some of the reasons why.