Cool features of Old English we've abandoned: The word for “have” was “habbe”. The opposite was “nabbe”. Same went for “will”, the opposite of which was “nill”. They would combine these, so willy-nilly means “whether you like it or not”.
Habbe-nabbe turned into hobnob, which used to mean “drinking socially”, for some reason.
Nabbe and nill were technically contractions of ne habbe and ne will, but their use was standardized and was considered to be mandatory in formal writing.
Like all the other Germanic languages, English used to have a word with the same origin as the German word Reich. This was mostly supplanted with words that end with -dom like kingdom, or with French words like duchy. It's still retained in the word “Bishopric” however.
Old English had the letters þ (thorn) and ð (eth), with both made th sounds, as well as the letter ȝ (yogh) which used to be in place of most of the gh's we have in words today (night → niȝt). It was pronounced a lot of ways. All were eliminated by the printing press.
Ȝ survived in the form of the letter Z in some Scottish names, like MacKenzie (which was pronounced like MacKenyie before people started reading it with a Z) and the island of Shetland, which was called Zetland as a result of this dead letter until 1975.
Old English did not use the letters K, Q, or Z. They are foreign invaders. All /k/ sounds were bravely provided by the letter C, with the few native /qu/ pairs rendered faithfully by cw, with “cwen” being the old word for “queen”
Alternately it was spelled cƿen, as Old English had another abandoned consonant that died out much earlier, Ƿ (wynn). Looking a lot like the letter P, this represented the /w/ sound as was based on the runic letter wunjo. ᚹ
Before the Latin Alphabet the Old English language was written in a set of modified Germanic runes called Futhorc. Despite being designed for the language, it required multiple digraphs that were used inconsistently to represent sounds there were no runes for.
Their use was unpopular in the century before the Norman conquest, but like everything else unique about Old English's orthography, they too were finally slain by wicked Norman scribes.
Despite their languages having evolved separately for over 600 years, Old English and Old Norse speakers did not need interpreters to talk with each other. Translators were mentioned as being required to speak to Irish monks or Roman bishops, but not with the Norse.
An Old English word for “god” was os, related to the Norse word Æsir. Its use was supplanted with God as the former had pagan connotations. It survived in the names Oscar and Oswald, which mean “God's Spear” and “God-ruler” respectively
England has dozens of places named after Woden, the chief god of the Old English pantheon and Anglo-Saxon version of Odin:
Old English personal names were functionally limitless because they were all made up of two elements that could be swapped out. Alfred was made up of ælf and ræd, which translated means something like “Counseled by Elves”. Beowulf means bee wolf and is figure of speech for “bear”.
Other “wolf” names include Æthelwulf (noble wolf, same origin as Adolf), Cynewulf (kingly wolf), Cuthwulf (familiar wolf), Oswulf (gods' wolf), Eadwulf (wealthy wolf).
Ead- was also seen in Eadward (guardian of wealth), Eadberht (wealthy and bright), Eadrad (wealthy planner).