elder: Elder ‘older’ [OE] is not, of course, the same word as elder the tree-name [OE]. The former began life in prehistoric Germanic as *althizon, the comparative form of *althaz ‘old’. Gradually, the vowel i had an effect on the preceding vowel a, and by Old English times the word had become eldra – hence modern English elder. The regularized form older appeared in the 16th century. The derivative elderly dates from the 17th century. The tree-name comes from Old English ellærn, a word whose origin is not known for certain (although it may perhaps be related to English alder). The intrusive d began to appear in the 14th century. => old
"more old," Old English (Mercian) eldra, comparative of eald, ald (see old); only English survival of umlaut in comparison. Superseded by older since 16c. Elder statesman (1921) originally was a translation of Japanese genro (plural).
type of berry tree, c. 1400, with excrescent -d- from earlier ellen, from Old English ellæn, ellærn "elderberry tree," origin unknown, perhaps related to alder, which at any rate might be the source of the -d-. Common Germanic, cognates: Old Saxon elora, Middle Low German elre, Old High German elira, German Eller, Erle. Related: Elderberry.
"elderly person, senior citizen," c. 1200, from Old English eldra "older person, parent; ancestor; chief, prince" (used in biblical translation for Greek presbyter); see elder (adj.). Compare German Eltern, Danish forældre, Swedish föräldrar "parents." The Old English for "grandfather" was ealdfæder.