Origins
The word 'such' appears to be a simple, irreducible function word, but etymological analysis reveals it to be a compound — a fossil of an older, more transparent expression that has been compressed by centuries of phonological wear. Understanding its formation illuminates a productive word-building pattern in the Germanic languages.
Old English 'swylc' (also spelled 'swilc,' 'swelc,' and 'swulc' across dialects) meant 'of that kind, of that sort, such.' It is a compound of two elements: 'swā' (so, in that manner) and 'līc' (like, having the form of, body). The literal meaning was 'so-formed' or 'having that appearance' — essentially, 'looking like that.' The same compound appears across the Germanic family: Gothic 'swaleiks,' Old Norse 'slíkr' (modern Icelandic 'slíkur,' Swedish 'slik'), Old High German 'sulīh' (modern German 'solch'), Old Frisian 'sullik,' and Old Saxon 'sulīk' (Dutch 'zulk'). All preserve the same recipe of 'so' plus 'like.'
The element 'līc' deserves attention. In Proto-Germanic, *līkam meant both 'body, physical form' and 'having the appearance of.' It is the ancestor of Modern English 'like' (similar to), the suffix '-ly' (originally '-lic,' meaning 'having the form of'), and the now-archaic 'lich' (a corpse, preserved in 'lychgate' — the roofed gate of a churchyard where a coffin rests). The connection between 'body' and 'likeness' is intuitive: to say something is 'like' another thing is to say it has the same body or form.
Proto-Indo-European Roots
This compounding pattern — demonstrative or interrogative plus *līkam — was highly productive in Proto-Germanic and produced several other common English words. 'Which' derives from Old English 'hwylc' (from *hwa + *līkam, 'who-like, of what form?'). 'Each' derives from Old English 'ǣlc' (from *aiwa + *līkam, 'ever-like, every one alike'). Even 'ilk' in the Scottish phrase 'of that ilk' preserves the same '-lic' element. So 'such,' 'which,' and 'each' are structurally parallel: they differ only in their first element (so, who, ever).
The phonological journey from Old English 'swylc' to Modern English 'such' involves several changes. The initial cluster 'sw-' was simplified: the 'w' was gradually lost after 's,' leaving just 's-.' The vowel shifted and shortened. Most importantly, the final '-lc' cluster underwent palatalization and affrication, becoming the '-tch' or '-ch' sound /tʃ/. This same process affected 'which' (from 'hwylc') and 'each' (from 'ǣlc'). Middle English spellings include 'such,' 'swich,' 'soche,' and 'suche,' reflecting regional variation.
In Modern English, 'such' functions as a determiner ('such a day'), a predeterminer ('such nice weather'), and occasionally as a pronoun ('such is life'). The construction 'such as' (meaning 'for example' or 'of the kind that') dates to Middle English. 'Such that' as a formal connective ('arranged such that') became standard in mathematical and logical writing.
Word Formation
The word carries subtle intensifying force in addition to its deictic (pointing) function. 'Such a beautiful day' means not just 'a day of that kind' but implies 'a day beautiful to that degree.' This intensifying use has grown over the centuries and is especially prominent in informal speech ('it was such a mess'). Some grammarians distinguish the 'kind' use from the 'degree' use, but historically they are two faces of the same compound: something is 'so-formed' either in type or in magnitude.
The survival of 'such' as a common everyday word — while its internal structure has become completely opaque to modern speakers — is a reminder that even the simplest-seeming English words often conceal compound origins that only etymology can reveal.