eldfather

The story

1. Old English · inherited fromeald fæder“grandfather, ancestor”
2. Middle English · inherited fromeldfader
3. English todayeldfather

From Middle English eldfader, variant of olde fader, from Old English eald fæder (“grandfather, ancestor”), equivalent to eld (“old”) + father. Cognate with Scots eldfader (“grandfather, father-in-law”), Old Frisian aldafeder (“grandfather”).