Last night my wife asked me (in the course of our O’Brian reading) where the word admiral comes from, and I gave her an off-the-cuff answer that was correct in essence (Arabic amir) but wrong on the details, as I discovered when I looked it up in the OED today. What astonished me was the length of the etymology: 1,341 words, with separate mini-etymologies for five different historical forms of the word and excursuses on “A further development in Latin,” “Further comments regarding Arabic models” (“It has been suggested that the presence of the final -al was caused or reinforced by Arabic al, the definite article which is also used in genitive constructions, but this is not borne out by the textual evidence in either Arabic or the Western languages”), “History of the title,” “Development of phrases,” “Development of secondary senses,” and “Development of forms”! I briefly wondered whether this was the longest etymology in the OED, but then I realized that was foolishness, and upon checking the Guide to the Third Edition of the OED discovered that (unsurprisingly) “The longest etymology section in the dictionary is the revised one at the verb to be.” So of course I went to that entry and discovered the etymology is a mind-boggling 9,672 words long, so long that it has its own table of contents, running from “1. General overview” to “3.7. Omission of auxiliary have in periphrastic tenses.” And there are 1,765 words (considerably more than the entire admiral etymology) before the table of contents! Here are the first few sentences:
The paradigm of the verb ‘to be’ in West Germanic languages in general shows forms derived from three unrelated Indo-European bases, in English itself perhaps forms derived from four Indo-European bases. These occur in sometimes overlapping, but generally distinct functions within the paradigm (see below), although there have been significant changes in these functions over time and in different varieties of English. The following notation is used in this entry to distinguish the different forms: (i) am/is-group: α (am), β (is), γ (Old English sind), δ (Old English sīe), ε (art), ζ (are); (ii) be-group: η (be); (iii) was-group: θ (was), ι (were). The present tense and non-finite forms are chiefly derived from two distinct bases.[...]
God bless and keep the OED!
Also, I submit for your edification the five-minute YouTube video What Color Is A Mirror? by Michael Stevens of Vsauce. You may think it has nothing to do with linguistics, but you’ll discover he discusses the Indo-European root that (putatively) lies behind both black and French blanc and Spanish blanco ‘white’ (and thus English blank). Unfortunately, the OED doesn’t agree with this (“on formal grounds the word could be from a base related to the Germanic bases of blank [...], but since this would give an expected meaning ‘shining, white’ there is an obvious semantic difficulty; many have sought to resolve this by hypothesizing that the word meaning ‘black’ originated as a past participle (with the meaning ‘burnt, blackened’) of a verb meaning ‘to burn (brightly)’ derived from this base…”), but they don’t dismiss it out of hand, and having inoculated you against taking his etymological remarks too seriously, I urge you to enjoy his explanation of mirrors and color.