The story
- Old English · inherited from*rihtfull
- Middle English · inherited fromrightful
- English todayrightful
From Middle English rightful, ryghtfull, riȝtful, from Old English *rihtfull (suggested by derivative unrihtfull (“unrightful”)), equivalent to right + -ful.
Etymology from Wiktionary, CC BY-SA 4.0.