Origins
The word 'if' is the primary conditional conjunction in English, introducing hypothetical, counterfactual, and uncertain propositions. Its etymology is notable both for a striking phonological change — the loss of an initial consonant — and for the genuine uncertainty surrounding its deeper origins.
It descends from Old English 'gif' (if, whether, in case that), from Proto-Germanic *jabai (if, when). The Old English form was pronounced approximately /jif/, with a palatal initial consonant written as 'g' in the Old English scribal convention where 'g' before front vowels represented /j/ (the 'y' sound). During the Middle English period, this initial /j/ was lost, a process visible in transitional spellings: 'yif,' 'yef,' and finally 'if.' By the fourteenth century, the consonant-less form had become standard.
The Proto-Germanic *jabai is well attested. Gothic preserves it most faithfully as 'jabai' (if, when), used frequently in Wulfila's fourth-century Bible translation. Old High German 'ibu' and 'oba' (if, whether) show the same root with different suffixation, and modern German 'ob' (whether, if) descends from this form. Dutch 'of' (or, whether) is another cognate, showing how the conditional sense can shade into disjunction — 'whether' and 'or' are related concepts (presenting alternatives).
Proto-Indo-European Roots
The deeper PIE etymology of *jabai remains disputed among historical linguists. One influential hypothesis connects it to the PIE root underlying Proto-Germanic *gebaną (to give), suggesting that a conditional clause is semantically 'a given' — something granted or conceded for the sake of argument. This would make 'if' and 'give' distant relatives, though the connection is speculative and not universally accepted. Another proposal links *jabai to a PIE interrogative or dubitative particle, but no consensus has been reached.
What is clear is that 'if' has been remarkably stable in its function despite its phonological changes. Old English 'gif' served the same conditional and dubitative roles that modern 'if' serves: introducing conditions ('gif þū bist Godes sunu' — if thou art God's son), marking uncertainty, and signaling hypothetical reasoning. The word 'whether,' now largely confined to indirect questions, was once a stronger competitor for the conditional function, but 'if' prevailed as the primary conditional marker.
The informal adjective 'iffy' (uncertain, doubtful), first attested in the 1930s, is one of the very few derivatives of 'if' — function words rarely generate new vocabulary, and the existence of 'iffy' is itself a linguistic curiosity, treating a grammatical particle as if it were a content word with describable qualities.