Origin and history of within

a Middle English merger of Old English in (prep.) "in, into, upon, on, at, among; about, during;" and Old English inne (adv.) "within, inside," from Proto-Germanic *in (source also of Old Frisian, Dutch, German, Gothic in, Old Norse i), from PIE root *en "in." The simpler form took on both senses in Middle English.

Sense distinction between in and on is from later Middle English, and nuances in use of in and at still distinguish British and American English (in school/at school). Sometimes in Middle English shortened to i.

The noun sense of "influence, access (to power or authorities)," as in have an in with, is first recorded 1929 in American English. to be in for it "certain to meet with something unpleasant" is from 1690s. To be in with "on friendly terms with" is from 1670s. Ins and outs "intricacies, complications of an action or course" is from 1660s. In-and-out (n.) "copulation" is attested from 1610s.

originally noting opposition, competition, entanglement, but in Middle English shifting to note association or connection; proximity, harmony, alliance.

It is from Old English wið "against, opposite, from;" also "toward, by, near." The sense shifted in Middle English to denote association, combination, and union, partly by influence of Old Norse cognate viðr "against," but also "toward, at," and also perhaps by association with Latin cum "with" (as in pugnare cum "fight with"). Also compare obsolete wine "friend," related to win "to strive, struggle, fight" (see win (v.)) probably on the notion of "comrade-in-arms."

In this sense denoting company or connection it replaced Old English mid, which survives as a prefix (as in midwife; see mid (prep.)). The original sense of "against, in opposition" is retained in compounds such as withhold, withdraw, withstand.

The Old English word is a shortened form related to the first element in widdershins, from Proto-Germanic *withro- "against" (source also of Old Saxon withar "against," Middle Dutch, Dutch weder, Dutch weer "again," Gothic wiþra "against, opposite").

This is reconstructed to be from PIE *wi-tero-, literally "more apart," suffixed form of *wi- "separation" (source also of Sanskrit vi "apart," Avestan vi- "asunder," Sanskrit vitaram "further, farther," Old Church Slavonic vutoru "other, second"). Compare widow (n.).

Phrase with child "pregnant" is recorded from c. 1200. With it "cool, hip, up-to-date" is recorded by 1931 in Black English. What's with? "what are the circumstances of or explanation for" is by 1940.

With and by are so closely allied in many of their uses that it is impossible to lay down a rule by which these uses may at all times be distinguished. The same may be said, but to a less extent, of with and through. [Century Dictionary, 1891]

French avec "with" was originally avoc, from Vulgar Latin *abhoc, from apud hoc, literally "with this."