Origin and history of tenfold

"1 more than nine, twice five; the number which is one more than nine; a symbol representing this number;" Old English ten (Mercian), tien (West Saxon), adjective and noun, from Proto-Germanic *tehun (source also of Old Saxon tehan, Old Norse tiu, Danish ti, Old Frisian tian, Old Dutch ten, Dutch tien, Old High German zehan, German zehn, Gothic taihun "ten"), from PIE root *dekm- "ten."

The meaning "ten o'clock" is from 1712. Sometimes used to indicate "a large number." The Texan's exaggerated ten-gallon hat is from 1919. To be ten feet tall "feeling extremely successful or confident" is by 1962. The ten-foot pole that you wouldn't touch something with (1909) was earlier a 40-foot pole; the notion is of keeping one's distance, as in the advice to use, when dining with the devil, a long spoon.

Ten-four "I understand, message received," is attested in popular jargon from 1962, from citizens band and emergency dispatch radio 10-codes (which were in use in U.S. by 1950). Ten-speed, "bicycle with ten gears" is by 1977.

multiplicative word-forming element attached to numerals, from Old English -feald, Northumbrian -fald, from Proto-Germanic *-falda- (cognates: Old Saxon -fald, Old Frisian -fald, Old Norse -faldr, Dutch -voud, German -falt, Gothic falþs), combining form of *falthan, from PIE *polt-, extended form of root *pel- (2) "to fold."

The same root yielded fold (v.) and perhaps also Greek -ploid, -plos and Latin -plus (see -plus). Native words with it have been crowded out by Latinate double, triple, etc., but it persists in manifold, hundredfold, etc.