This is the 37th most frequent Icelandic word.
okkur
"Us" (accusative or dative form of "we" in Icelandic).
The word 'okkur' is used here in its accusative form to indicate the plural first-person pronoun with the verb 'langar', reflecting a desire or longing.
Okkur langar í ís.
We want ice cream.
In this sentence, 'okkur' is in its dative form, representing the indirect object in a construction where the teacher is giving something to the group (us).
Kennarinn gaf okkur verkefnið.
The teacher gave us the assignment.
Here, 'okkur' is again used in its accusative form as it acts as the object of the verb 'hjálpaði', which means 'helped'.