ifyoudaoicibaDictYouDict[if 词源字典]
if: [OE] The Old English version of if was gif, but its initial g was closer to modern English y in pronunciation than to g, and the conjunction gradually evolved through Middle English yif to if. It is not known where it ultimately came from; it is evidently connected with Old High German iba ‘condition’ and Old Norse ef ‘doubt’, but whether it started life as a noun like these or was from the beginning a conjunction is not clear. Its surviving Germanic relatives are German ob ‘whether’ and Dutch of ‘if’.
[if etymology, if origin, 英语词源]
if (conj.)youdaoicibaDictYouDict
Old English gif (initial g- in Old English pronounced with a sound close to Modern English -y-), from Proto-Germanic *ja-ba (cognates: Old Saxon, Old Norse ef, Old Frisian gef, Old High German ibu, German ob, Dutch of "if, whether"), from PIE pronominal stem *i- [Watkins]; Klein, OED suggest probably originally from an oblique case of a noun meaning "doubt" (compare Old High German iba "condition, stipulation, doubt," Old Norse if "doubt, hesitation," Swedish jäf "exception, challenge"). As a noun from 1510s.