Probably North Germanic origin. This etymology is incomplete. You can help Wiktionary by elaborating on the origins of this term. (UK, US) IPA(key): /læɡ/ Rhymes:...
1909, OCLC 11192831, quoted in The Case of Miss Elliott (ebook no. 2000141h.html), Australia: Project Gutenberg of Australia, February 2020: “H'm !” he said...