This is something I’ve always wondered about, but never really investigated, but thanks to the wonder of the internet and a few clicks of my mouse I found this

Surname: Elgey

Recorded in several spellings as shown below, this unusual and interesting surname is English and of pre 7th century origins. It is one of the variant forms of the surname created from the Middle English personal name “Alger”. This name is a result of the “falling together” of several names of different origins, including Old English, Anglo-Saxon and laterafter the conquest of 1066, Norman-French. The final element of all of them is “gar or ger”, both meaning a spear, while the first element is usually “alb”, meaning elf or “adal”, noble, or “ald”, old, resulting in such names as “Aelfgar” (elf-spear), “Aethelgar” (nobel-spear) and “Ealdgar” (old-spear). The modern surname spellings include Algar, Algore, Algy, Elgar, Elgy, Elgey, Elgee and others. Early examples of recordings taken from surviving church registers of the city of London include John Elgee who was christened at St James Clerkenwell in 1667 and William Elgy christened at All Souls Marylebone, on June 27th 1852. The first recorded spelling of the family name is shown to be that of Robert Elger. This was dated 1271, in the “Ancient Deeds of Norfolk”, during the reign of King Henry 111, known as “The Frenchman”, 1216 – 1272. Surnames became necessary when governments introduced personal taxation. In England this was sometimes known as the Poll Tax. Throughout the centuries, surnames in every country have continued to “develop” often leading to astonishing variants of the original spelling.