German orthography
Compound words, including nouns, are written together, e.g. "Haustür" (Haus+Tür; house door), "Tischlampe" (Tisch+Lampe; table lamp), "Kaltwasserhahn" (Kalt+Wasser+Hahn; cold water tap/faucet). This can lead to long words: the longest word in regular use, "Rechtsschutzversicherungsgesellschaften" ("legal protection insurance companies"), consists of 39 letters; while the longest German word ever published ("Donaudampfschiffahrtselektrizitätenhauptbetriebswerkbauunterbeamtengesellschaft", "Association for subordinate officials of the head office management of the Danube steamboat electrical services") has 79 letters.
Proto-Germanic language
By the end of the Proto-Germanic period, word-final long vowels were shortened to short vowels. Following that, overlong vowels were shortened to regular long vowels in all positions, merging with originally long vowels except word-finally (because of the earlier shortening), so that they remained distinct in that position. This was a late dialectal development, because the end result was not the same in all Germanic languages: word-final "ē" shortened to "a" in East and West Germanic but to "i" in Old Norse, and word-final "ō" shortened to "a" in Gothic but to "o" (probably ) in early North and West Germanic, with a later raising to "u" (the 6th century Salic law still has "maltho" in late Frankish).