behave: [15] To ‘behave oneself’ originally meant literally to ‘have oneself in a particular way’ – have being used here in the sense ‘hold’ or ‘comport’. The be- is an intensive prefix. Of particular interest is the way in which the word preserves in aspic the 15th-century pronunciation of have in stressed contexts. For much of its history behave has been used with reference to a person’s bearing and public dignity (‘He was some years a Captain, and behaved himself with great gallantry in several engagements’, Richard Steele, Spectator Number 2, 1711), and the modern connotations of propriety, of ‘goodness’ versus ‘naughtiness’, are a relatively recent, 19th-century development.
The noun behaviour [15] was formed on analogy with the verb from an earlier haviour, a variant of aver ‘possession’ [14], from the nominal use of the Old French verb aveir ‘have’. => have
early 15c., from be- intensive prefix + have in sense of "to have or bear (oneself) in a particular way, comport" (compare German sich behaben, French se porter). Cognate Old English compound behabban meant "to contain," and alternatively the modern sense of behave might have evolved from behabban via a notion of "self-restraint." Related: Behaved; behaving.
