Koe means: You.
Koe is one of the singular pronouns in te reo Māori:
There are different pronouns used if you’re referring to 2 people or 2+ people. These plural pronouns generally behave quite regularly in form (rules applying to one often apply to all, duals end in ‘-ua’, plurals end in ‘-tou’) but the singular pronouns are irregular.
When used with the prepositions mā, nā, mō, nō, a, and o (which generally relate to possession) the singular pronouns take special forms appended to these prepositions:
So you would have ‘for us’ - mā mātou, ‘for them’ - mā rātou, but you would not use ‘mā koe’ for ‘for you’ and would instead use māu, appending the second person singular suffix to mā.