Hi there,

"Komið!", "Farið!", Come!, Go!. Here -ið refers to "þið" you plural.

"Kom þú" goes "said more friendly or less formal" "komdu". þú
singular.
Also "Far þú" goes "Farðu". thee
We say and spell komdu instead of komðu
for sake of euphony I reckon.
I also reckon "D" or "edd" goes in for "eðð" (eth) as "edd" were aid.

eth's aid.

thanks Uoden