The story
- Old English · inherited fromlangsumlīċe“long, during or for a long time; patiently, with long-suffering”
- Middle English · inherited from*langsumliche
- English todaylongsomely
From Middle English *langsumliche, from Old English langsumlīċe (“long, during or for a long time; patiently, with long-suffering”), equivalent to longsome + -ly.
Etymology from Wiktionary, CC BY-SA 4.0.