'Only' is Old English for 'one-like' — literally 'having the form of being sole, without another.'
From Old English 'ānlīc' (unique, solitary, without equal), a compound of 'ān' (one, sole) + 'līc' (like, having the form of, body) — literally 'one-like' or 'having the form of being one.' The adverbial form was 'ānlīce.' Both derive from the same Proto-Germanic *ainaz (one), which traces to PIE *óynos (one, single, unique). This foundational numeral spawned a remarkable family in English: 'one' itself, 'a/an' (the indefinite article — a reduced form of 'one'), 'once' (one time), 'alone' (all + one, originally 'all one' meaning wholly by oneself), 'atone' (to be 'at one' with someone, to reconcile), 'eleven' (from Proto-Germanic *ainlif, 'one left' after counting ten), and 'none' (Old English 'nān,' not one). 'Only' is therefore the 'one-ly' — 'in the