Wit, unker, git: The lost medieval pronouns of English intimacy
www.bbc.com
Tales of love and adventure from 1,000 years ago reveal a dazzling range of now-extinct English pronouns. They capture something unique about how people once thought about "two-ness".

It’s a bit of pop linguistics about the dual number in English, with a few inaccuracies, but it’s interesting regardless. I’ll provide here some further historical info.

Proto-Indo-European contrasted three grammatical numbers: singular, dual, and plural. With the dual being used mostly for things that come in pairs (like arms or a couple). By Proto-Germanic times, the dual only survived in the pronouns, as you can see in this table:

Person/number Nominative Accusative Oblique Possessive
1SG (“I”) ek~ik mek~mik miz mīnaz
1DU (“we both”) wet~wit unk unkiz unkeraz
1PL (“we”) wīz~wiz uns unsiz unseraz
2SG (“thou”) θū θek~θik θiz θīnaz
2DU (“you two”) jut~jit inkw inkwiz inkweraz
2PL (“y’all”) jūz~jīz izwiz izwiz izweraz
reflexive (“self”) se- sek~sik siz sīnaz

Note those forms are reconstructed (I didn’t want to clutter the table with asterisks). That ⟨θ⟩ is to be read as in “think”, ⟨j⟩ as in “yes”, and the vowels as in Spanish or Polish, with a mācron making them lōnger (longcat is looooong lōng).

The dual pronouns would survive until Early Middle English (up to 1350), but were increasingly less used. I believe most of the other pronouns from that table survived.