The story
- Proto-Germanic · inherited from*langiþō
- Proto-West Germanic · inherited from*langiþu
- Old English · inherited fromlengþ
- Middle English · inherited fromlengthe
- English todaylength
From Middle English lengthe, from Old English lengþ, lengþu, from Proto-West Germanic *langiþu, from Proto-Germanic *langiþō, equivalent to long + -th (abstract nominal suffix). Cognate with Scots lenth, lainth (“length”), Saterland Frisian Loangte (“length”), West Frisian lingte, langte (“length”), Dutch lengte (“length”), German Low German Längde, Längd, Längte, Längt (“length”), Danish længde (“length”), Swedish längd (“length”), Icelandic lengd (“length”).
Etymology from Wiktionary, CC BY-SA 4.0.