quattrocento n.

"1 more than three, twice two; the number which is one more than three; a symbol representing this number;" Old English feower "four; four times," from Proto-Germanic *fedwores (source also of Old Saxon fiuwar, Old Frisian fiower, fiuwer, Frankish *fitter-, Dutch vier, Old High German fior, German vier, Old Norse fjorir, Danish fire, Swedish fyra, Gothic fidwor "four"), from PIE root *kwetwer- "four." The phonetic evolution of the Germanic forms has not been fully explained; Watkins explains the -f- as being from the following number (Modern English five).

To be on all fours is from 1719; earlier on all four (14c.). Four-letter word as a euphemism for one of the short words generally regarded as offensive or objectionable is attested from 1923; four-letter man is recorded from 1920 (apparently as a euphemism for a shit). Compare Latin homo trium litterarum, literally "three-letter man," a euphemism for fur "a thief." A four-in-hand (1793) was a carriage drawn by four horses driven by one person; in the sense of "loosely tied necktie" it is attested from 1892. To study The History of the Four Kings (1760, compare French Livres des Quatre Rois) contains an old euphemistic slang phrase for "a pack of cards," from the time when card-playing was considered a wicked pastime for students. Slang 4-1-1 "essential information" (by 1993) is from the telephone number called to get customer information. The four-color problem so called from 1879. The four-minute mile was attained 1954.

"1 more than ninety-nine, ten times ten; the number which is one more than ninety-nine; a symbol representing this number;" Old English hundred "the number of 100, a counting of 100," from Proto-Germanic *hunda-ratha- (source also of Old Frisian hundred, Old Saxon hunderod, Old Norse hundrað, German hundert); first element is Proto-Germanic *hundam "hundred" (cognate with Gothic hund, Old High German hunt), from PIE *km-tom "hundred," reduced from *dkm-tom- (source also of Sanskrit satam, Avestan satem, Greek hekaton, Latin centum, Lithuanian šimtas, Old Church Slavonic suto, Old Irish cet, Breton kant "hundred"), suffixed form of root *dekm- "ten."

The second element is Proto-Germanic *rath "reckoning, number" (as in Gothic raþjo "a reckoning, account, number," garaþjan "to count;" from PIE root *re- "to reason, count"). The common word for the number in Old English was simple hund, and Old English also used hund-teontig.

In Old Norse hundrath meant 120, that is the long hundred of six score, and at a later date, when both the six-score hundred and the five-score hundred were in use, the old or long hundred was styled hundrath tolf-roett ... meaning "duodecimal hundred," and the new or short hundred was called hundrath ti-rætt, meaning "decimal hundred." "The Long Hundred and its use in England" was discussed by Mr W.H. Stevenson, in 1889, in the Archæological Review (iv. 313-27), where he stated that amongst the Teutons, who longest preserved their native customs unimpaired by the influence of Latin Christianity, the hundred was generally the six-score hundred. The short hundred was introduced among the Northmen in the train of Christianity. [Transactions of the Lancashire and Cheshire Antiquarian Society, 1907]

Meaning "division of a county or shire with its own court" (still in some British place names and U.S. state of Delaware) was in Old English and probably represents 100 hides of land. The Hundred Years War (which ran intermittently from 1337 to 1453) was first so called in 1874. The original Hundred Days was the period between Napoleon's restoration and his final abdication in 1815.