number (n.)
c.1300, "sum, aggregate of a collection," from Anglo-French noumbre, Old French nombre and directly from Latin numerus "a number, quantity," from PIE root *nem- "to divide, distribute, allot" (related to Greek nemein "to deal out;" see nemesis). Meaning "symbol or figure of arithmetic value" is from late 14c. Meaning "single (numbered) issue of a magazine" is from 1795. The meaning "musical selection" (1885) is from vaudeville theater programs, where acts were marked by a number. Meaning "dialing combination to reach a particular telephone receiver" is from 1879; hence wrong number (1886).

Number one "oneself" is from 1704 (mock-Italian form numero uno attested from 1973); the biblical Book of Numbers (c.1400, Latin Numeri, Greek Arithmoi) so called because it begins with a census of the Israelites. Slang number one and number two for "urination" and "defecation" attested from 1902. Number cruncher is 1966, of machines; 1971, of persons. To get or have (someone's) number "have someone figured out" is attested from 1853. The numbers "illegal lottery" is from 1897, American English.
number (v.)
c.1300, "to count," from Old French nombrer "to count, reckon," from nombre (n.) "number" (see number (n.)). Meaning "to assign a number to" is late 14c.; that of "to ascertain the number of" is from early 15c. Related: Numbered; numbering.