Í tollinum spurði starfsmaðurinn hvaðan við værum að koma.

This is a very common Icelandic word-order pattern.

Icelandic is a V2 language in main clauses, which means the finite verb usually comes in second position. If you put a time/place expression first, the verb still has to stay second.

So:

• Í tollinum spurði starfsmaðurinn ... = At customs, the employee asked ...

Here the first slot is Í tollinum, so the verb spurði comes next, and the subject starfsmaðurinn comes after it.

A more neutral order is also possible:

• Starfsmaðurinn spurði í tollinum ...

But the original sentence emphasizes the setting: at customs.

Í tollinum means in customs or at customs.

The noun is:

• tollur = customs, customs office, customs control

Here it appears as tollinum, which is:

• dative singular
• with the definite article attached

So:

• tollur = a customs office / customs
• tollinum = the customs office / the customs area

Why dative? Because í can take either:

• accusative for movement into
• dative for location in

Compare:

• í tollinn = into customs
• í tollinum = in/at customs

Since the sentence describes where the asking happened, Icelandic uses the dative.

The ending -inn is the definite article attached to the noun.

So:

• starfsmaður = employee, staff member
• starfsmaðurinn = the employee / the staff member

This is very typical in Icelandic. Instead of using a separate word like English the, Icelandic usually attaches the article to the end of the noun.

A rough breakdown:

• starfs = work-related / staff-
• maður = man, person
• starfsmaður = employee
• starfsmaðurinn = the employee

Yes.

• spyrja = to ask
• spurði = asked

So starfsmaðurinn spurði means the employee asked.

This is simply the past tense form used for a completed action in the past.

Hvaðan means from where or more naturally where ... from.

So:

• hvar = where
• hvaðan = where from
• þangað = to there / there to
• þar = there
• þaðan = from there

In this sentence:

• hvaðan við værum að koma = where we were coming from

So the question is about origin, not just location.

Compare:

• Hvar ert þú? = Where are you?
• Hvaðan ertu að koma? = Where are you coming from?

This is one of the most important grammar points in the sentence.

• við vorum = we were
• við værum = we were / would be, in the subjunctive

Here Icelandic uses the subjunctive because the clause is an indirect question after a past-tense verb:

• spurði = asked
• then the reported question: hvaðan við værum að koma

This is very natural Icelandic after verbs like ask, say, know, wonder, especially in reported speech or indirect questions.

Direct question:

• Hvaðan eruð þið að koma? = Where are you coming from?

Reported indirectly in the past:

• Hann spurði hvaðan við værum að koma. = He asked where we were coming from.

English does not mark this difference clearly, so it often feels strange to learners, but in Icelandic the subjunctive is very common here.

Værum is a form of vera (to be).

Specifically, it is:

• past subjunctive
• 1st person plural
• meaning we were in this context

So:

• vera = to be
• værum = we were (subjunctive)

Even though English just says were, Icelandic is making a grammatical distinction here.

Because it is an embedded question or indirect question, not a direct question.

Direct question:

• Hvaðan værum við að koma?
  or more naturally in everyday speech:
• Hvaðan eruð þið að koma?

But after a verb like spurði, Icelandic uses statement-like word order inside the subordinate clause:

• Hann spurði hvaðan við værum að koma.

So the order is:

• question word: hvaðan
• subject: við
• verb: værum

This is similar to English:

• Direct: Where are you coming from?
• Indirect: He asked where we were coming from.

Notice English also stops using direct-question inversion in the indirect version.

Yes, literally að koma means to come, but here it is part of the expression:

• vera að koma = to be coming

So:

• við værum að koma = we were coming

With hvaðan, the full sense is:

• hvaðan við værum að koma = where we were coming from

This is a very common Icelandic way to express an ongoing or current action, somewhat like English be + -ing.

Compare:

• Ég er að borða. = I am eating.
• Við erum að fara. = We are leaving.
• Þau voru að koma. = They were coming.

Sometimes Icelandic can express similar ideas without vera að + infinitive, but in this sentence vera að koma is very natural and idiomatic.

• að koma emphasizes the action/process: coming
• With hvaðan, it gives the natural sense coming from

So hvaðan við værum að koma is a very normal way to say where we were coming from.

A learner should treat vera að + infinitive as a very useful everyday pattern.

Yes, við means we.

That is exactly what Icelandic needs here, because við is the subject of the embedded clause:

• hvaðan við værum að koma = where we were coming from

Even though English sometimes makes learners think in terms of object forms after certain verbs, this clause still has its own subject and verb, so Icelandic uses the subject form við.

Yes:

• Í = in, at
• tollinum = the customs area / the customs office (dative singular of tollur with article)
• spurði = asked
• starfsmaðurinn = the employee / the staff member
• hvaðan = from where, where ... from
• við = we
• værum = were (past subjunctive of vera)
• að koma = coming / to come

So the structure is:

• At customs,
• the employee asked
• where we were coming from.

The key takeaways are:

1. V2 word order in main clauses

   • Í tollinum spurði starfsmaðurinn ...
   • If a place phrase comes first, the verb comes second.

2. Prepositions can control case

   • í
     • dative for location: í tollinum

3. Definite article is attached

   • starfsmaðurinn = the employee
   • tollinum = in the customs / at the customs area

4. Indirect questions use subordinate-clause word order

   • hvaðan við værum ...
   • not direct-question inversion

5. Subjunctive in reported/indirect speech

   • værum after spurði

6. vera að + infinitive

   • værum að koma = were coming

If you understand those six points, you understand most of what makes this sentence interesting.