Uncertain, but likely from Proto-Celtic *Londinjon (“place that ﬂoods”), from Proto-Indo-European *lendʰ- (“to sink; subdue”) + *-injo-, a suffix forming specific nouns and found in other Romano-Celtic placenames. Cognate to Proto-Celtic *landā (“low-lying land”), whence Old Irish land, Welsh llan, as well as *londos (“subduing > fierce”, adj.), whence Old Irish lond.
An earlier, more difficult proposal derives it from *Plowonidonjon, morphologically adapted from a pre-Celtic Indo-European substrate word meaning something like “Boat River, Unfordable River” or “Flooding-River” and made up of Proto-Indo-European *plew- (“to flow”) and a disputed *neyd- (“to flow”).
Forms in -don- could be artificial Latinizations modelled after e.g. Old English Wreocen < Latin Viroconium (modern Wroxeter). Appears as Middle Welsh Llundein, Old English Lunden, which may not continue the Classical Latin form, but may continue Late British Latin *Lundeinju if the medial -i- of the original word was short. Cf. Etymology of London.
- Lundinium, Londonium, Lundonium, Londonum, Londinum (Late and Medieval Latin)
- Lundonia, Londonia, Lundoniae (Medieval Latin, as sg. or pl.)
- (Classical) IPA(key): /lonˈdi.ni.um/, [ɫ̪ɔn̪ˈd̪ɪniʊ̃ˑ]
- (Ecclesiastical) IPA(key): /lonˈdi.ni.um/, [lɔn̪ˈd̪iːnium]
- Note: the length of the medial /i/ is unattested, but is likely to have been short.
Second-declension noun (neuter), with locative, singular only.
1Found in older Latin (until the Augustan Age).
- → Ancient Greek: Λονδίνιον (Londínion)
- → Old English: Lunden
- → English: Londinium
- → German: London
- Sicilian: Lònnira
- Peter Schrijver (2013) Language Contact and the Origins of the Germanic Languages, Routledge, →ISBN, pages 54-57
- ^ Richard Coates (1998), “A New Explanation of the Name of London”, in Transactions of the Philological Society, volume 96, issue 2, DOI:10.1111/1467-968X.00027, ISSN 1467-968X, page 203–229